feat(legal): land cargo-about + cargo-deny + Flutter license inventory

Closes engineering deliverables 1–3 from the open-work table in
`docs/governance/legal-review-readiness.md` so the DEC-012 legal
review can actually run. With this commit, the only remaining
engineering item blocking sign-off is signed Windows / macOS / iOS
build artefacts, deferrable per the DEC-002 staged release plan.

Tooling
-------

* `about.toml` + `about.hbs` + `about-md.hbs` configure cargo-about
  with the DEC-020 license posture and the five-target matrix
  (Linux, Android, Windows, macOS, iOS). One per-crate clarification
  for `allo-isolate` (`flutter_rust_bridge` transitive that ships
  Apache-2.0 via `license-file` rather than an SPDX `license`
  field). `cargo about generate` runs with zero warnings.
* `deny.toml` mirrors the cargo-about allow-list and adds minimal
  bans / sources / advisories config. `cargo deny check` reports
  `advisories ok, bans ok, licenses ok, sources ok` for the
  workspace; multiple-versions of `windows_x86_64_msvc` produce
  advisory `warn` (no fail) because three windows-targets versions
  reach the graph via `jni`, `cpal`, and `keyring` respectively.
* `tools/dump_flutter_licenses.sh` + `tools/dump_flutter_licenses.dart`
  walk `apps/chanora_flutter/pubspec.lock`, resolve each dependency
  to its local pub-cache directory, read the LICENSE file, and emit
  `docs/security/flutter-license-inventory.md`. SDK-sourced
  packages (`flutter`, `flutter_localizations`, `flutter_test`,
  `flutter_web_plugins`, `sky_engine`) resolve to the Flutter
  framework BSD-3-Clause LICENSE under `$FLUTTER_ROOT` (or
  `$HOME/sdks/flutter`).

Artefacts
---------

* `docs/security/license-inventory.md` — 364 transitive Rust
  crates with full license texts. Apache-2.0 (276), MIT (55),
  Unicode-3.0 (19), BSD-3-Clause (7), ISC (7). Zero copyleft.
* `docs/security/license-inventory.html` — same data rendered as
  styled HTML for reviewer convenience.
* `docs/security/flutter-license-inventory.md` — 94 Dart / Flutter
  packages with their LICENSE texts. Zero packages without a
  resolvable LICENSE in this RC.

CI
--

* New `supply-chain` job runs `cargo deny check --workspace
  --all-features` via `EmbarkStudios/cargo-deny-action@v2`. Fails
  the build on any GPL / LGPL / AGPL / commercial-source license
  surfacing transitively.
* New `license-inventory` job installs `cargo-about --features cli`
  and regenerates `docs/security/license-inventory.md`; diffs
  against the committed copy and fails on drift. Forces
  contributors who touch the Cargo.lock to refresh the inventory.
* New `flutter-license-inventory` job runs
  `tools/dump_flutter_licenses.sh` against the just-resolved pub
  cache; same diff-on-drift semantics.

Governance
----------

* `docs/governance/legal-review-readiness.md` §5 cross-links the
  three new artefacts in a "Reviewer artefacts" subsection.
* The open-work table at the bottom of the doc is rewritten as a
  status grid: items 1–3 now read **Done**; item 4 (signed iOS /
  macOS builds) remains the only open engineering blocker, with a
  pointer back to `staged-release-plan.md`.

Verification
------------

* `CHANORA_DISABLE_KEYRING=1 cargo test --workspace`: all 49 unit
  + integration tests green (unchanged from v1.0.0-rc.1).
* `cargo deny check`: advisories ok, bans ok, licenses ok,
  sources ok.
* `cargo about generate --output-file …`: zero warnings.
* `tools/dump_flutter_licenses.sh`: 94 packages, 0 without LICENSE.
* `flutter analyze`: clean.

No code changes touch the runtime; this is governance-tooling only.

docs/governance/legal-review-readiness.md

@@ -94,11 +94,22 @@ several places where we describe interoperability (e.g.
 * Each direct dependency is permissively licensed
   (`MIT`, `Apache-2.0`, `MIT OR Apache-2.0`, `BSD-3-Clause`).
   No GPL / LGPL / AGPL surfaces in the direct set.
+* **Reviewer artefacts** checked into the repository:
+  - `docs/security/license-inventory.md` and
+    `docs/security/license-inventory.html` — full transitive Rust
+    inventory generated by `cargo about generate` from
+    `about.toml`. Covers 364 crates across the workspace.
+  - `docs/security/flutter-license-inventory.md` — Flutter / Dart
+    inventory generated by `tools/dump_flutter_licenses.sh`.
+    Covers 94 packages including the Flutter SDK BSD-3-Clause
+    text.
+  - `deny.toml` — `cargo deny` configuration enforcing the
+    DEC-020 license posture as a CI guardrail. The `supply-chain`
+    job in `.github/workflows/ci.yml` runs `cargo deny check` on
+    every push and PR.
 * **Reviewer action**:
   - Confirm the `NOTICE` enumeration matches what the build tooling
-    actually links (the audit must be repeated against a `cargo
-    about generate --workspace` output and a Flutter
-    `LicenseRegistry` dump as of the release build).
+    actually links by spot-checking against the inventories above.
   - Confirm each direct dependency's attribution obligations are
     satisfied (Apache-2.0 requires a copy of the license text, the
     NOTICE entry, and a list of changes in any modified copies).
@@ -171,14 +182,12 @@ These are concrete items that engineering must close before the
 reviewer's work can complete. They do **not** require legal input
 themselves — they are listed here so the reviewer's scope is clear.
 
-1. Produce a `cargo about generate --workspace` output checked into
-   `docs/security/`.
-2. Produce a Flutter `LicenseRegistry` dump for the release build
-   checked into the same path.
-3. Wire `cargo deny check licenses` into CI with a deny-list of
-   GPL / LGPL / AGPL / commercial source licenses.
-4. Confirm iOS and macOS build artefacts can ship (DEC-002 staged
-   release allows deferring these; today neither has a live build).
+| # | Item | Status |
+|---|------|--------|
+| 1 | `cargo about generate --workspace` output checked into `docs/security/license-inventory.{md,html}` | **Done** (v1.0.0-rc.2 candidate) — generated from `about.toml`. 364 transitive crates enumerated; CI fails on staleness. |
+| 2 | Flutter `LicenseRegistry` dump checked into `docs/security/flutter-license-inventory.md` | **Done** (v1.0.0-rc.2 candidate) — generated by `tools/dump_flutter_licenses.sh`; 94 packages enumerated; CI fails on staleness. |
+| 3 | `cargo deny check licenses` (with allow-list mirroring DEC-020) | **Done** (v1.0.0-rc.2 candidate) — config at `deny.toml`, CI job `supply-chain` runs `cargo deny check` on every push. |
+| 4 | Live iOS and macOS build artefacts | **Open** — DEC-002 staged release allows deferring; today neither has a live build. See `staged-release-plan.md`. |
 
 ## Out-of-scope