docs(library-selection): apply CodeRabbit follow-ups from PR #208 (#209)

Five inline review findings from CodeRabbit on PR #208. All addressed.
None changes runtime behaviour.

## Changes

- `crates/fbuild-build/tests/teensylc_acceptance.rs` — drop substring
  fallback for `setup`/`loop` symbol probes. They're `extern "C"` from
  the sketch and exact `has_symbol(...)` is sufficient; the substring
  match was overly permissive (4-5-char tokens collide with mangled
  C++ names like `_ZN6Stream8setupXxx`).
- `crates/CLAUDE.md` — add "Diagnostic subcommand exception" pattern
  to clarify that `clang-tidy` / `clang-query` / `iwyu` / `mcp` /
  `lnk` / `lib-select` intentionally bypass the daemon. Prevents
  future readers from concluding `lib-select` violates the
  "thin HTTP client" rule.
- `docs/architecture/library-selection.md` — update top-of-doc status
  block and "Future work" list to reflect that PR #208 shipped Phase 6
  acceptance gates and Phase 8.a `lib-select` CLI; only Phase 4
  (zccache#130), Phase 7, and Phase 8.b cleanup remain. The "Tests"
  section now points at the actual `tests/*_acceptance.rs` files
  rather than describing them as future work.

## CodeRabbit comment 2 — false positive (no change)

CodeRabbit flagged `use fbuild_packages::Framework;` in
`crates/fbuild-cli/src/lib_select.rs:25` as unused. Verified: the
`Framework` trait is required for method-call dispatch on the 12+
framework objects the file constructs (`get_libraries_dir()` is a
trait method). Removing the import produces 12× E0599 errors. Kept.

Refs: #205, #208

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: zackees

crates/CLAUDE.md

@@ -48,6 +48,8 @@ fbuild-test-support (test utilities) ──────────────
 
 **HTTP API boundary:** CLI sends JSON requests to daemon over HTTP. Build output streams via WebSocket. Serial monitor data streams via `/ws/serial-monitor`. All endpoints match the Python FastAPI daemon's contract.
 
+**Diagnostic subcommand exception:** A small, growing set of `fbuild-cli` subcommands (`clang-tidy`, `clang-query`, `iwyu`, `mcp`, `lnk`, `lib-select`) run in-process and intentionally bypass the daemon. They are read-only diagnostics that don't need build orchestration, so a round-trip through the HTTP API would only add latency. The "thin HTTP client" rule still applies to every command that touches the build pipeline (`build`, `deploy`, `monitor`, `test-emu`, etc.).
+
 **PyO3 consumer contract:** FastLED imports `SerialMonitor` as a Python context manager with `read_lines()`, `write()`, `write_json_rpc()`. The `fbuild-python` crate must preserve this API exactly.
 
 ## Current Status

crates/fbuild-build/tests/teensylc_acceptance.rs

@@ -73,8 +73,7 @@ fn teensylc_blink_meets_205_acceptance_criteria() {
     }
     for required in ["setup", "loop"] {
         assert!(
-            probe.has_symbol(required).expect("symbol query")
-                || probe.has_symbol_containing(required).expect("symbol query"),
+            probe.has_symbol(required).expect("symbol query"),
             "A-11: required symbol '{required}' missing from ELF"
         );
     }

docs/architecture/library-selection.md

@@ -1,8 +1,9 @@
 # Library selection (LDF-style)
 
 > Status: foundation phases (0–3 + Phase 5 framework_libs delegation) landed
-> in PR #207. Phase 4 (zccache memoization) tracked at zackees/zccache#130.
-> Phase 6 acceptance gates and Phase 7 perf gates are follow-ups in #205.
+> in PR #207. Phase 6 acceptance gates and Phase 8.a `lib-select` CLI landed
+> in PR #208. Phase 4 (zccache memoization) tracked at zackees/zccache#130.
+> Phase 7 perf gates and Phase 8.b cleanup remain follow-ups in `#205`.
 
 ## Why
 
@@ -127,20 +128,21 @@ keys safe.
 - Resolver tests in `crates/fbuild-library-select/src/lib.rs` including
   the #204 regression guard, sort-stability, missing-include-dir
   tolerance, and same-basename-different-library disambiguation.
-- Acceptance tests for AC#1 (teensyLC), AC#4 (stm32 SPI auto-discovery)
-  land in Phase 6 via `fbuild-test-support`'s `MiniFramework`,
-  `ElfProbe`, and `CompileDb` utilities.
+- Acceptance gates for AC#1 (teensyLC) and AC#4 (stm32 SPI
+  auto-discovery) live in `crates/fbuild-build/tests/`
+  (`teensylc_acceptance.rs`, `stm32_acceptance.rs`). They are
+  `#[ignore]`'d by default and run by CI with `--ignored`. They use
+  `fbuild-test-support`'s `ElfProbe` and `CompileDb` utilities to probe
+  the produced firmware.
 
 ## Future work
 
 - **Phase 4** — zccache K/V memoization. Gated on zackees/zccache#130
   shipping a versioned `KvStore` API and a 1.4.0 release; see
   `tasks/zccache-kv-design.md`.
-- **Phase 6** — wire ELF + compile-DB probes through `fbuild-test-support`
-  into per-board acceptance tests, gating CI on AC#1..#4 from #205.
 - **Phase 7** — perf gates wired into `bench/fastled-examples`.
-- **Phase 8** — `fbuild lib-select --explain` CLI subcommand and final
-  deletion of `framework_libs.rs` helpers.
+- **Phase 8.b** — final deletion of any dead helpers in `framework_libs.rs`
+  once Phase 4 cache lands.
 
 ## References