docs(cli): note requires: [...] fail-fast on missing provider package (#1597)

`os start` "What it boots" listed `requires: [...]` auto-registration but
predated the intent-driven fail-fast behavior. Clarify that a declared
service capability whose provider package isn't installed aborts boot
(fail-fast), and call out that `auth`/`ui` are the tier-gated exceptions
with their own opt-in rules.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TjHfkKmEvgk8v7N8nTe5sH

Author: claude

content/docs/getting-started/cli.mdx

@@ -315,7 +315,7 @@ os start
 
 **What it boots:**
 - Reads the artifact's `manifest`, `objects`, `views`, `flows`, …
-- Auto-registers the platform services declared in `requires: [...]` (e.g. `ai`, `automation`, `analytics`, `auth`, `ui`)
+- Auto-registers the platform services declared in `requires: [...]` (e.g. `ai`, `automation`, `analytics`, `auth`, `ui`). Declaring a **service** capability (`automation`, `analytics`, `ai`, `audit`, …) is a *requirement*: if its provider package isn't installed, boot **fails fast** with a clear error instead of silently starting without a capability you asked for. (`auth` and `ui` are tier-gated with their own opt-in rules — `auth`'s secret-gated skip is described below.)
 - Auto-detects the driver from the database URL scheme (`memory://` → in-memory, `libsql://`/`https://` → Turso, `postgres[ql]://`/`pg://` → pg, `mongodb[+srv]://` → MongoDB, otherwise sqlite)
 - Runs standalone boot mode with one active environment.