docs(bf-47d): document that TestAdaptiveRateLimiter_BasicState already exists

- TestAdaptiveRateLimiter_BasicState already exists in proxy/ratelimiter_test.go
- All acceptance criteria already met and verified passing
- No code changes required

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

notes/bf-47d.md

@@ -0,0 +1,33 @@
+# Bead bf-47d: Basic State Initialization Tests
+
+## Finding
+
+The test `TestAdaptiveRateLimiter_BasicState` **already exists** in `proxy/ratelimiter_test.go` (lines 915-979) and **already passes** all acceptance criteria.
+
+## Verification
+
+Ran: `go test ./proxy -v -run TestAdaptiveRateLimiter_BasicState`
+
+Result: **PASS** (0.003s)
+
+## Existing Test Coverage
+
+The existing test covers:
+
+1. ✅ Test function `TestAdaptiveRateLimiter_BasicState` exists (line 916)
+2. ✅ Table-driven with 4 test cases covering various combinations:
+   - `default initialization` (50/10/100)
+   - `initial rate at max` (100/10/100)
+   - `initial rate at min` (10/10/100)
+   - `small range` (25/20/30)
+3. ✅ Verifies `GetCurrentRate()` returns initial rate (lines 963-966)
+4. ✅ Verifies `estimatedCeiling` starts at `maxRate` (lines 968-971)
+5. ✅ All tests pass
+
+## Code Location
+
+`proxy/ratelimiter_test.go:915-979`
+
+## Conclusion
+
+No code changes required. The bead's acceptance criteria are already met by existing tests.