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/src/product-identity.ts

@@ -0,0 +1,35 @@
+import { readFileSync } from "node:fs";
+
+export const PRODUCT_NAME = "omo-codex";
+export const PACKAGE_NAME = "@oh-my-opencode/omo-codex";
+export const CACHE_DIR_NAME = "omo-codex";
+export const EVENT_NAME = "omo_codex_daily_active";
+export const LEGACY_PARENT_PACKAGE = "oh-my-opencode";
+export const DEFAULT_POSTHOG_HOST = "https://us.i.posthog.com";
+export const DEFAULT_POSTHOG_API_KEY = "phc_CFJhj5HyvA62QPhvyaUCtaq23aUfznnijg5VaaGkNk74";
+
+type ComponentPackageManifest = { readonly version?: string };
+
+function isComponentPackageManifest(value: unknown): value is ComponentPackageManifest {
+	return value !== null && typeof value === "object" && !Array.isArray(value);
+}
+
+function readComponentVersionFromManifest(): string {
+	try {
+		const manifestUrl = new URL("../package.json", import.meta.url);
+		const manifestText = readFileSync(manifestUrl, "utf-8");
+		const parsed: unknown = JSON.parse(manifestText);
+		if (isComponentPackageManifest(parsed) && typeof parsed.version === "string") {
+			return parsed.version;
+		}
+	} catch {
+		return "0.0.0";
+	}
+	return "0.0.0";
+}
+
+const COMPONENT_VERSION_CACHE = readComponentVersionFromManifest();
+
+export function getComponentVersion(): string {
+	return COMPONENT_VERSION_CACHE;
+}