feat(omo-codex): wire Codex SessionStart telemetry for DAU/WAU/MAU

Adds a new Codex plugin component `telemetry` that emits a single
omo_codex_daily_active event (reason: session_start) from every Codex
SessionStart hook, with the same UTC-day deduplication, hashed
installation identifier, and four-flag opt-out as the install-time
event. Previously omo-codex telemetry only fired on install_completed,
so DAU/WAU/MAU under-reported real Codex usage.

- New plugin component packages/omo-codex/plugin/components/telemetry/
  mirrors the rules/comment-checker/lsp pattern: own src/, tsc build,
  vitest tests, package.json (posthog-node dep), hooks/hooks.json.
- src/codex-hook.ts wraps createPluginPostHog().trackActive(..., "session_start")
  with safeShutdown so Codex session startup never blocks on telemetry.
- Plugin root hooks.json + workspaces register the new component
  alongside rules and ultrawork on SessionStart.
- Aggregate test expectations updated to include the telemetry directory.
- cross-package-equivalence.test.ts pins product-identity constants and
  shouldDisablePostHog behavior to stay byte-equivalent between the CLI
  installer (src/telemetry/) and the plugin runtime
  (plugin/components/telemetry/src/), so the two PostHog sources never
  drift on event name, distinct_id base, dedup file path, or opt-out
  flags.
- PostHogActivityReason union in the CLI-side posthog.ts gains
  "session_start" so future CLI paths can emit the same reason without
  a type break.

packages/omo-codex/plugin/components/telemetry/biome.json

@@ -0,0 +1,48 @@
+{
+	"$schema": "https://biomejs.dev/schemas/2.4.15/schema.json",
+	"linter": {
+		"enabled": true,
+		"rules": {
+			"recommended": true,
+			"style": {
+				"noDefaultExport": "error",
+				"noEnum": "error",
+				"noNonNullAssertion": "error",
+				"useImportType": "error",
+				"useConst": "error",
+				"useNodejsImportProtocol": "off"
+			},
+			"complexity": {
+				"useLiteralKeys": "off"
+			},
+			"suspicious": {
+				"noExplicitAny": "error",
+				"noTsIgnore": "error",
+				"noControlCharactersInRegex": "off",
+				"noEmptyInterface": "off"
+			}
+		}
+	},
+	"formatter": {
+		"enabled": true,
+		"formatWithErrors": false,
+		"indentStyle": "tab",
+		"indentWidth": 3,
+		"lineWidth": 120
+	},
+	"files": {
+		"includes": ["src/**/*.ts", "test/**/*.ts", "vitest.config.ts", "!**/node_modules/**/*", "!**/dist/**/*"]
+	},
+	"overrides": [
+		{
+			"includes": ["vitest.config.ts"],
+			"linter": {
+				"rules": {
+					"style": {
+						"noDefaultExport": "off"
+					}
+				}
+			}
+		}
+	]
+}