chore: changelog, exclude list, wasm support, slim tokio features

- Add CHANGELOG.md (Keep a Changelog format) covering 0.1.1 and 0.1.0
- Exclude AGENTS.md from the published crate (docs/reviews/ and
  docs/sdd_process.md were already excluded)
- Slim tokio features: full → rt, sync, time, io-util, macros (no
  net/fs/process usage in the crate)
- Enable wasm32-unknown-unknown: uuid rng-getrandom + getrandom 0.4
  wasm_js so request-ID generation works on wasm
- Add wasm + semver-checks to AGENTS.md pre-release verification

Verification:
- cargo test: 543 passed, 0 failed
- cargo clippy --all-targets -- -D warnings: clean
- cargo fmt --check: clean
- cargo doc --no-deps: clean
- cargo check --target wasm32-unknown-unknown: clean
- cargo clippy --target wasm32-unknown-unknown -- -D warnings: clean
- cargo semver-checks check-release: 196 pass, no semver update required
- cargo publish --dry-run --allow-dirty: succeeds (103 files, 1.8MiB)

AGENTS.md

@@ -203,6 +203,15 @@ cargo publish --dry-run --allow-dirty         # before a release
 If feature flags are added, also run `cargo test --all-features` and
 `cargo clippy --all-features --all-targets -- -D warnings`.
 
+Before a release, also verify the wasm target (the crate is
+WASM-clean by construction — no net/fs/process tokio features):
+
+```bash
+cargo check --target wasm32-unknown-unknown
+cargo clippy --target wasm32-unknown-unknown -- -D warnings
+cargo semver-checks check-release             # before a release
+```
+
 ## Architecture Context
 
 - `docs/architecture/` — the authoritative spec. Read it before