refactor(hls): trust the upload server URL verbatim, drop withExtensionHint

Policy shift agreed with the server-side collaborator: the URL the
NIP-96 / Blossom server returns is already the optimal form — clean
Content-Type, correct cache keys, range-friendly — and the client
should not second-guess it. Stripping extensions, appending hints or
rewriting to bare sha256 all add round trips and cache misses for no
real win now that the WordPress plugin returns clean <hash>.m3u8 URLs.

Concretely:
- HlsUploadPipeline drops the withExtensionHint helper entirely. Every
  combinedUrl / mediaPlaylistUrl / masterUrl flows straight from the
  uploader's MediaUploadResult.url into the playlist rewrite and the
  HlsUploadResult.
- A small kdoc note at the top of the pipeline documents the policy
  ("if a server returns an unplayable URL, the fix is server-side").

Pipeline tests pruned:
- appendsMp4HintToBareCombinedUrlInMediaPlaylist — removed, was testing
  the appender that no longer exists.
- appendsM3u8HintToBarePlaylistUrlInMasterPlaylist — removed, same.
- trailingDotUrlsAreSanitisedIntoCleanExtension — removed, the Nip96
  fallback-extension map keeps the server from returning trailing-dot
  URLs in the first place.
- doesNotDoubleAppendExtensionWhenAlreadyPresent — removed.

Kept and reframed:
- serverUrlsAlreadyWithExtensionPassThroughUntouched — the canonical
  contract: server returns clean .m3u8 / .mp4, pipeline forwards
  verbatim.
- bareServerUrlsPassThroughVerbatim (new) — explicitly documents that
  even a bare-hash URL flows through unchanged; the pipeline does not
  try to make it playable.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

amethyst/src/main/java/com/vitorpamplona/amethyst/service/uploads/hls/HlsUploadPipeline.kt

@@ -58,6 +58,12 @@ data class HlsUploadedRendition(
  * Finally rewrites the master playlist to reference the per-rendition playlist URLs and uploads
  * the master. The resulting [HlsUploadResult] is what the publisher uses to build the NIP-71
  * event.
+ *
+ * URL handling policy: the pipeline uses the URL the server returned verbatim. No extension is
+ * appended, no trailing dot stripped, no bare-hash rewriting. The server is responsible for
+ * returning a URL that the player can fetch as-is — that way we get the best cache coherence,
+ * correct Content-Type, clean range requests, and no double round trips. If a server returns an
+ * unplayable URL, the fix is server-side.
  */
 class HlsUploadPipeline(
     private val uploader: HlsBlobUploader,
@@ -75,10 +81,7 @@ class HlsUploadPipeline(
                 val combined = uploader.upload(rendition.combinedFile, CONTENT_TYPE_VIDEO_MP4)
                 onProgress(++done, total)
                 val combinedUrl =
-                    withExtensionHint(
-                        combined.url ?: error("Uploader returned null URL for ${rendition.combinedFile.name}"),
-                        CONTENT_TYPE_VIDEO_MP4,
-                    )
+                    combined.url ?: error("Uploader returned null URL for ${rendition.combinedFile.name}")
 
                 val rewrittenMedia =
                     HlsPlaylistRewriter.rewrite(
@@ -90,10 +93,7 @@ class HlsUploadPipeline(
                 val mediaPlaylist = uploader.upload(mediaPlaylistFile, CONTENT_TYPE_HLS)
                 onProgress(++done, total)
                 val mediaPlaylistUrl =
-                    withExtensionHint(
-                        mediaPlaylist.url ?: error("Uploader returned null URL for media playlist ${rendition.label}"),
-                        CONTENT_TYPE_HLS,
-                    )
+                    mediaPlaylist.url ?: error("Uploader returned null URL for media playlist ${rendition.label}")
 
                 HlsUploadedRendition(
                     label = rendition.label,
@@ -112,10 +112,7 @@ class HlsUploadPipeline(
         val master = uploader.upload(masterFile, CONTENT_TYPE_HLS)
         onProgress(++done, total)
         val masterUrl =
-            withExtensionHint(
-                master.url ?: error("Uploader returned null URL for master playlist"),
-                CONTENT_TYPE_HLS,
-            )
+            master.url ?: error("Uploader returned null URL for master playlist")
 
         return HlsUploadResult(
             masterUrl = masterUrl,
@@ -124,28 +121,6 @@ class HlsUploadPipeline(
         )
     }
 
-    // Blossom servers typically return bare-hash URLs (https://server/<sha256>), but HLS parsers
-    // and ExoPlayer's Util.inferContentType sniff the URL extension to pick the right source
-    // factory. Append a hint unless the upload server already baked one in. Trailing dots are
-    // trimmed and any pre-existing doubled extension (e.g. "..m3u8") collapsed, so a server that
-    // echoes our empty-extension upload filename does not produce unreachable URLs.
-    private fun withExtensionHint(
-        url: String,
-        contentType: String,
-    ): String {
-        val ext =
-            when (contentType) {
-                CONTENT_TYPE_VIDEO_MP4 -> ".mp4"
-                CONTENT_TYPE_HLS -> ".m3u8"
-                else -> return url
-            }
-        val sanitised =
-            url
-                .replace(Regex("""\.{2,}""" + Regex.escape(ext.trimStart('.')) + "$", RegexOption.IGNORE_CASE), ext)
-                .trimEnd('.')
-        return if (sanitised.endsWith(ext, ignoreCase = true)) sanitised else sanitised + ext
-    }
-
     companion object {
         const val CONTENT_TYPE_VIDEO_MP4 = "video/mp4"
         const val CONTENT_TYPE_HLS = "application/vnd.apple.mpegurl"

amethyst/src/test/java/com/vitorpamplona/amethyst/service/uploads/hls/HlsUploadPipelineTest.kt

@@ -180,36 +180,25 @@ class HlsUploadPipelineTest {
     }
 
     @Test
-    fun appendsMp4HintToBareCombinedUrlInMediaPlaylist() {
-        val bundle = createBundle(listOf("360p"))
-        val uploader = BareUrlUploader()
-        val pipeline = HlsUploadPipeline(uploader)
-
-        runBlocking { pipeline.upload(bundle) }
-
-        val uploadedMediaPlaylist = uploader.calls[1].third
-        assertTrue(
-            "media playlist should reference url with .mp4 hint",
-            uploadedMediaPlaylist.contains("https://blossom.test/bare-1.mp4"),
-        )
-        assertTrue(!uploadedMediaPlaylist.contains("https://blossom.test/bare-1\""))
-    }
-
-    @Test
-    fun appendsM3u8HintToBarePlaylistUrlInMasterPlaylist() {
+    fun bareServerUrlsPassThroughVerbatim() {
+        // Policy: the pipeline uses whatever URL the server returned, unchanged.
+        // Even a bare-hash URL with no extension flows straight into the rewritten
+        // playlists. If it does not play, the fix is server-side (return a playable URL).
         val bundle = createBundle(listOf("360p"))
         val uploader = BareUrlUploader()
         val pipeline = HlsUploadPipeline(uploader)
 
         val result = runBlocking { pipeline.upload(bundle) }
 
-        val uploadedMaster = uploader.calls[2].third
+        assertEquals("https://blossom.test/bare-1", result.renditions[0].combinedUrl)
+        assertEquals("https://blossom.test/bare-2", result.renditions[0].playlistUrl)
+        assertEquals("https://blossom.test/bare-3", result.masterUrl)
+        // The rewritten media playlist that the server received must contain the bare url.
+        val uploadedMediaPlaylist = uploader.calls[1].third
         assertTrue(
-            "master playlist should reference playlist url with .m3u8 hint",
-            uploadedMaster.contains("https://blossom.test/bare-2.m3u8"),
+            "media playlist should reference bare url: $uploadedMediaPlaylist",
+            uploadedMediaPlaylist.contains("https://blossom.test/bare-1"),
         )
-        assertEquals("https://blossom.test/bare-3.m3u8", result.masterUrl)
-        assertEquals("https://blossom.test/bare-1.mp4", result.renditions[0].combinedUrl)
     }
 
     @Test
@@ -252,46 +241,6 @@ class HlsUploadPipelineTest {
         assertTrue(!result.renditions[0].playlistUrl.contains(".m3u8.m3u8"))
     }
 
-    @Test
-    fun trailingDotUrlsAreSanitisedIntoCleanExtension() {
-        val bundle = createBundle(listOf("360p"))
-        val uploader =
-            object : HlsBlobUploader {
-                var count = 0
-
-                override suspend fun upload(
-                    file: File,
-                    contentType: String,
-                ): MediaUploadResult {
-                    count++
-                    return MediaUploadResult(url = "https://blossom.test/bare-$count.", sha256 = "sha-$count", size = file.length())
-                }
-            }
-        val pipeline = HlsUploadPipeline(uploader)
-
-        val result = runBlocking { pipeline.upload(bundle) }
-
-        assertTrue("masterUrl must not contain '..': ${result.masterUrl}", !result.masterUrl.contains(".."))
-        assertTrue("masterUrl must not end with '.': ${result.masterUrl}", !result.masterUrl.endsWith("."))
-        assertTrue(result.masterUrl.endsWith(".m3u8"))
-        assertTrue(!result.renditions[0].combinedUrl.contains(".."))
-        assertTrue(result.renditions[0].combinedUrl.endsWith(".mp4"))
-    }
-
-    @Test
-    fun doesNotDoubleAppendExtensionWhenAlreadyPresent() {
-        val bundle = createBundle(listOf("360p"))
-        val uploader = FakeUploader() // returns urls ending in .mp4 / .m3u8
-        val pipeline = HlsUploadPipeline(uploader)
-
-        runBlocking { pipeline.upload(bundle) }
-
-        val uploadedMediaPlaylist = uploader.calls[1].content
-        assertTrue(!uploadedMediaPlaylist.contains(".mp4.mp4"))
-        val uploadedMaster = uploader.calls[2].content
-        assertTrue(!uploadedMaster.contains(".m3u8.m3u8"))
-    }
-
     @Test
     fun reportsUploadProgressPerStep() {
         val bundle = createBundle(listOf("360p", "540p"))