feat(photon): gRPC-native iMessage channel (no webhook)

Make Photon iMessage a first-class persistent-connection channel like
Discord/Slack, using the spectrum-ts gRPC stream for both directions.

- Inbound: the sidecar forwards the SDK's app.messages gRPC stream to the
  adapter over a loopback GET /inbound (NDJSON) instead of webhooks. Drops
  the aiohttp webhook server, HMAC signature verification, public URL, and
  PHOTON_WEBHOOK_* config; adapter reconnects with backoff.
- Management plane: device login uses client_id=photon-cli against the
  single dashboard host (Bearer), matching the official photon-hq/cli;
  find-or-create "Hermes Agent" project, enable Spectrum, rotate secret,
  register user (with phone dedup), surface the assigned iMessage line.
- SDK projectId is the project's spectrumProjectId, not the dashboard id;
  runtime creds persist to ~/.hermes/.env like every other channel.
- CLI: 6-step setup, webhook subcommands removed.
- Tests/docs updated for the gRPC flow; sidecar pins spectrum-ts ^1.17.1.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/plugins/platforms/photon/test_mention_gating.py

@@ -22,7 +22,6 @@ from plugins.platforms.photon.adapter import PhotonAdapter
 def _make_adapter(monkeypatch: pytest.MonkeyPatch, extra: dict | None = None) -> PhotonAdapter:
     monkeypatch.setenv("PHOTON_PROJECT_ID", "test-project-id")
     monkeypatch.setenv("PHOTON_PROJECT_SECRET", "test-project-secret")
-    monkeypatch.delenv("PHOTON_WEBHOOK_SECRET", raising=False)
     monkeypatch.delenv("PHOTON_REQUIRE_MENTION", raising=False)
     monkeypatch.delenv("PHOTON_MENTION_PATTERNS", raising=False)
     cfg = PlatformConfig(enabled=True, token="", extra=extra or {})
@@ -31,27 +30,21 @@ def _make_adapter(monkeypatch: pytest.MonkeyPatch, extra: dict | None = None) ->
 
 def _group_payload(text: str) -> dict:
     return {
-        "event": "messages",
-        "message": {
-            "id": f"grp-{abs(hash(text))}",
-            "timestamp": "2026-05-14T19:06:32.000Z",
-            "sender": {"id": "+15551234567"},
-            "space": {"id": "any;+;group-guid-xyz"},
-            "content": {"type": "text", "text": text},
-        },
+        "messageId": f"grp-{abs(hash(text))}",
+        "space": {"id": "group-guid-xyz", "type": "group", "phone": None},
+        "sender": {"id": "+15551234567"},
+        "content": {"type": "text", "text": text},
+        "timestamp": "2026-05-14T19:06:32.000Z",
     }
 
 
 def _dm_payload(text: str) -> dict:
     return {
-        "event": "messages",
-        "message": {
-            "id": f"dm-{abs(hash(text))}",
-            "timestamp": "2026-05-14T19:06:32.000Z",
-            "sender": {"id": "+15551234567"},
-            "space": {"id": "any;-;+15551234567"},
-            "content": {"type": "text", "text": text},
-        },
+        "messageId": f"dm-{abs(hash(text))}",
+        "space": {"id": "+15551234567", "type": "dm", "phone": "+15551234567"},
+        "sender": {"id": "+15551234567"},
+        "content": {"type": "text", "text": text},
+        "timestamp": "2026-05-14T19:06:32.000Z",
     }
 
 
@@ -126,7 +119,6 @@ def test_custom_mention_patterns_from_config(monkeypatch: pytest.MonkeyPatch) ->
 def test_mention_patterns_env_comma_separated(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setenv("PHOTON_PROJECT_ID", "test-project-id")
     monkeypatch.setenv("PHOTON_PROJECT_SECRET", "test-project-secret")
-    monkeypatch.delenv("PHOTON_WEBHOOK_SECRET", raising=False)
     monkeypatch.setenv("PHOTON_REQUIRE_MENTION", "true")
     monkeypatch.setenv("PHOTON_MENTION_PATTERNS", r"bot\b, assistant\b")
     cfg = PlatformConfig(enabled=True, token="", extra={})