0.3.0 Track A: attribute cache + publish_* wired

[avrabe]

Summary

RsMatterBridge::publish_reading and publish_alert no longer call unimplemented!(). They now translate the wohl event to the right Matter cluster + attribute (via the cluster mapping table from PR #27 + B1 fix), apply the unit conversion (per DESIGN.md §7.4), and write the typed value into a thread-safe in-memory cache.

This is the push side of the push/pull mediation the architecture critic flagged in PR #29 and that the AADL c_attr comment documents. The pull side (rs-matter DataModelHandler reading from this cache when a controller subscribes) is the next slice — same one that registers per-zone/contact/circuit endpoints with the right device-type descriptors.

What this PR ships

File	Change
src/cache.rs (new)	AttributeKey, AttributeValue { Bool / Int16 / Int64 / Float32 }, AttributeCache = Mutex<HashMap<...>> with set/get/len/is_empty. Shareable as Arc<AttributeCache>. 4 unit tests.
src/conversion.rs (new)	convert_reading + convert_alert implementing the DESIGN.md §7.4 table: Temperature saturating cast, Power × 1000 (saturating), Concentration as f32, BooleanState bool. Alert-without-value semantics: Bool(true) on boolean clusters (the alert IS the trigger), None on numeric clusters (caller skips cache update). 10 unit tests.
src/rs_matter.rs	RsMatterBridge gains Arc<AttributeCache> field + .cache() accessor. publish_* are now real: lookup mapping → convert → set cache. 6 new integration tests.
src/lib.rs	Declares cache + conversion modules (not feature-gated; both work without rs-matter).

Test counts

cargo +1.87.0 test -p wohl-matter-bridge --lib                34/34  (was 19, +15)
cargo +1.87.0 test -p wohl-matter-bridge
  --features rs-matter-backend --lib                          43/43  (was 22, +21)

Oracles

cargo +1.87.0 fmt -p wohl-matter-bridge --check               OK
cargo +1.87.0 clippy -p wohl-matter-bridge -D warnings        OK (no features)
cargo +1.87.0 clippy ... --features rs-matter-backend         OK
cargo +1.87.0 test --workspace                                all binaries pass
cargo kani -p wohl-alert                                      4/4 harnesses
spar analyze (StarterHome.Deployed)                           0 errors
rivet validate                                                PASS

What's NOT in this PR (still)

• The cache is written but not yet read by rs-matter. A commissioned controller subscribing to a bridged attribute today still sees only the root endpoint clusters (Basic Information, General Commissioning, Operational Credentials). The next slice wires:
  • Per-zone/contact/circuit Matter endpoint registration with the right device-type descriptor (ContactSensor 0x0015, WaterLeakDetector 0x0043, etc. per DESIGN.md §2),
  • A custom DataModelHandler that pulls from this cache when rs-matter asks for an attribute value,
  • The endpoint-id allocation policy decision (DESIGN.md §7.1 open question — u16 space, tagged-high-byte or register-on-demand).
• The cache infrastructure stands on its own merits today: publish_* is non-panicking, the conversion contract is unit-tested, and the cache is observable from the bridge owner for test rigs or operator debug commands.

Verified line: still untouched

Zero edits to crates/wohl-{leak,temp,air,door,power,alert,ota,fw-door-bench}/, proofs/verus/, or fuzz/. Kani 4/4 on wohl-alert.

Test plan

• CI green across all 14 jobs.
• After merge: slice 6 — DataModelHandler + endpoint registration + cache-pull integration.

🤖 Generated with Claude Code