docs(bf-3cu6j): miroir-proxy build green — compile-fix step is a no-op

Step 4 of 4 (FINAL). Verified the build directly (real cargo, not the
PATH wrapper): `cargo build -p miroir-proxy` exits 0, incl. a forced
recompile after touching search.rs (8.84s, zero errors/warnings). No
uncommitted source changes exist (only .beads bookkeeping), so there
were no compile errors to fix — no-op. No logic changes made.

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

notes/bf-3cu6j.md

@@ -0,0 +1,57 @@
+# bf-3cu6j — Fix compile errors in changed code (step 4 of 4, FINAL)
+
+Split-child of **bf-146g8**, step 4 of 4 (FINAL). **COMPILE FIXES ONLY.**
+
+## Task
+
+If step 3 (bf-13wyf) build already exited 0 → this is a **no-op**:
+record "build was already green" and close. If it failed → fix *only*
+compile errors in the changed code (search.rs / test / CHANGELOG), no
+logic rewrite of `extract_source_ip` / rate-limit code, then re-run
+`cargo build -p miroir-proxy` until exit 0.
+
+## Result: BUILD ALREADY GREEN — NO-OP
+
+Step 3 (bf-13wyf) recorded **exit 0**. This step re-verified directly rather
+than trusting the prior note.
+
+### Verification (real cargo, not the wrapper)
+
+`$HOME/.cargo/bin/cargo` (symlink → rustup) — i.e. the *real* cargo, not the
+PATH wrapper that redirects stderr to `/dev/null`.
+
+1. Incremental build:
+   ```
+   Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.17s
+   exit 0
+   ```
+2. Forced recompile to rule out a stale cache — `touch`ed
+   `crates/miroir-proxy/src/routes/search.rs` (the file this task names) and
+   rebuilt:
+   ```
+   Compiling miroir-proxy v0.1.0 (/home/coding/miroir/crates/miroir-proxy)
+   Finished `dev` profile [unoptimized + debuginfo] target(s) in 8.84s
+   exit 0
+   ```
+   The crate genuinely recompiled (8.84s) with **zero errors and zero warnings**.
+
+### Why there is nothing to fix
+
+- The working tree has **no uncommitted source changes** — only `.beads/`
+  bookkeeping (`issues.jsonl`, `.needle-predispatch-sha`) and untracked trace
+  dirs. No diff to `search.rs`, no new test, no CHANGELOG entry.
+- Per bf-5izsg (step 2), the rate-limit *functionality* in `search.rs` is
+  **pre-existing committed code** (~6 weeks old), not a new in-progress fix.
+  There is no half-applied change that could be broken.
+- The `touch` in step 2 above changed only mtime, not content — the working
+  tree is unaffected.
+
+## Acceptance criteria
+
+- [x] `cargo build -p miroir-proxy` exits 0 (verified twice, incl. forced recompile).
+- [x] No behavioral/logic rewrite of extraction or rate-limit code — none was
+      needed; no compile errors existed to fix.
+
+## Conclusion
+
+Build is green. **No-op.** No code edits made in this step.