fix(nests): align kind-4312 + kind-30312 wire format with nostrnests/EGG-07

After verifying the nostrnests reference (NestsUI-v2 @ main):
- ProfileCard.tsx writes kicks as ['action','kick'] tags with empty content
- useAdminCommands.ts reads action via tags.find(t => t==='action') and
  applies a 60-s relay since plus a processedRef Set to dedup re-deliveries
- p-tag role marker for moderators is 'admin', not 'moderator'

Amethyst was diverging on every one of those, which means our outbound
admin commands were invisible to nostrnests, theirs to us, and any
nostrnests admin (role='admin') failed our isModerator() / canSpeak()
gates entirely — kicks and force-mutes signed by them were silently
dropped.

Changes:

quartz/AdminCommandEvent.kt
  - Emit ['action', '<verb>'] tag with empty content
  - Reader prefers the tag, falls back to content for any in-flight
    Amethyst-built kick from before this commit
  - kick() and forceMute() share a common build() helper

quartz/ParticipantTag.kt
  - ROLE.MODERATOR.code = 'admin' (matches nostrnests + EGG-07)
  - Adds legacyCodes = ['moderator'] so older Amethyst-emitted
    kind-30312 events still parse as MODERATOR
  - effectiveRole() walks both code + legacyCodes

amethyst/AdminCommandsCollector
  - Filter carries since = now - 60 (EGG-07 #7)
  - Defensive per-event freshness re-check for cached events / clock skew
  - mutableSetOf<String>() processed-id dedup for the lifetime of the
    collector, mirroring useAdminCommands.ts's processedRef

EGG-07.md
  - Documents the Amethyst-only ['action','mute'] extension under a new
    'Implemented extensions' section. nostrnests doesn't emit or honour
    it today; cross-client force-mutes only work between Amethyst peers
  - 'warn' stays in the future-actions list — nostrnests has no plans
    for it either

Tests:
  - ParticipantTagTest: new asserts that 'admin' / 'Admin' / 'ADMIN'
    parse as ROLE.MODERATOR; pins the wire string to 'admin' and the
    legacy alias to 'moderator'
  - AdminCommandEventTest: kick/forceMute templates carry ['action', _]
    tag with empty content; legacy content-form still parses; tag wins
    over content when both are present

nestsClient/specs/EGG-07.md

@@ -170,3 +170,13 @@ moderation without speaking to the relay.
 
 Future EGGs MAY introduce additional `action` values (e.g. `"mute"`,
 `"warn"`). Implementers MUST treat unknown actions as no-ops.
+
+### Implemented extensions
+
+Amethyst additionally emits and honours `["action", "mute"]` as a
+host-issued *force-mute*: the targeted speaker's client flips its own
+mic-mute (the `["muted", "1"]` flag on its next kind:10312 heartbeat)
+and stops broadcasting audio. nostrnests' web client does not yet
+emit or recognise this verb, so cross-client force-mutes only land
+when both sides run a client that implements it. Authority gates,
+freshness window, and replay rules are identical to `kick`.