docs: document the Core-tier gate (15 default / 29 with FAF_TOOLS=all)

The README said "29 tools" and never mentioned the Core-tier surface shipped in
a68fb1c. Reflect the real default (15 Core advertised; full 29 via FAF_TOOLS=all,
every tool still callable by name). Lands in the next release — which is what
actually refreshes the Glama listing, since Glama scans the latest tag/release
(currently the pre-gate v2.2.1), not main HEAD.

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

Author: Wolfe-Jam

README.md

@@ -106,7 +106,7 @@ faf bi-sync --all
 faf_git { url: "https://github.com/facebook/react" }
 ```
 
-**29 MCP tools** (with CLI fallback) · **309 tests** (9 suites) · **7 bundled parsers**
+**Core tier:** 15 essential tools shown by default; set `FAF_TOOLS=all` for the full **29** (every tool stays callable by name either way) · with CLI fallback · **9 test suites** · **7 bundled parsers**
 
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