Make CLI success output copy-paste-safe; add --serve, docs hub, key hygiene

A successful clone printed a bare, timestamped app path that wrapped mid-word
in the terminal, so users' `cd` failed and `npm install && npm run dev` ran in
the wrong directory — a confusing failure from a successful clone. Plus there
was no first-party "see it locally" path, no central docs page, "clone" was
conflated with `git clone`, and key hygiene wasn't stated.

CLI (compiler):
- Add compiler/src/cliSummary.ts: a copy-paste-safe success block on stderr — a
  single QUOTED `cd "<app>" && npm install && npm run dev` line that survives
  terminal wrapping — plus the AGENTS.md safe-to-edit pointers (content.ts,
  components/). The machine-readable {"event":"done",...} JSON stays on stdout.
- Add --serve (npm install + npm run dev in the generated app) and --open
  (also open the browser at the detected dev URL). Wired into single + multi.
- Add writeLatestPointer(): refresh a runs/<site>/latest symlink to the newest
  run so there's a stable, timestamp-free cd/script target. The reuse/regen
  scanners already filter to digit-prefixed run dirs, so `latest` is ignored.
- Tests: cliSummary (quoting, single-line command, Next/Vite roots, stable-path
  preference, --serve/--open hint) and runsLayout (symlink write + in-place
  refresh, timestamp-free stable path).

Docs:
- Add docs/README.md as a central documentation index.
- State prominently that ditto "cloning" = generating a codebase from a live
  URL, NOT `git clone` (no source repo required), in README + docs hub.
- Add "keys are secrets: use $DITTO_API_KEY, never inline/commit, rotate
  anytime" beside the key/auth examples in README + docs/SERVICE.md.
- Document --serve/--open and the latest symlink in README + compiler/README.

Note: the live ditto.site/docs web route and the dashboard's inline-token
snippet live in the marketing-site repo and still need a change there.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/SERVICE.md

@@ -89,6 +89,11 @@ GET    /healthz                    → { ok: true }  (unauthenticated)
 
 `/v1/clones*` and `/mcp` are authenticated when `API_KEYS` is set or DB-backed
 keys exist. Use `Authorization: Bearer <key>` or `x-api-key: <key>`.
+
+> **Treat keys as secrets.** In any snippet you copy or share, template the key as
+> an environment variable (`Authorization: Bearer $DITTO_API_KEY`) rather than an
+> inline `dtto_live_...` token — inline keys leak into shell history, logs, and
+> pasted transcripts. Never commit a key; rotate a leaked one from the dashboard.
 Signup routes are intentionally public only when `SIGNUP_ENABLED=true` **and**
 `DATABASE_URL` is set. Direct `POST /v1/signup` mints a `dtto_live_...` key
 immediately when `SIGNUP_DIRECT_ENABLED=true`. For public production signup,