chore: prepare 0.8.24 release

[leehack]

Summary

Prepare llamadart 0.8.24 from current main to ship the fresh macOS Flutter dependency-scanning fix (#491), preserve physical iOS speech-test failure-phase diagnostics (#489), and keep repository writer checks independent of generated website output (#493, resolving #487). This patch adds no public API or runtime pin changes.

Production-readiness scope

• Eight existing metadata files: core version, pub-generated chat-app lock, both current changelogs, and four installation README/docs pages. Runtime behavior is unchanged by this PR.
• Native llama.cpp v0.4.0, Web bridge v0.1.43, native LiteRT v0.16.0-native.2, Web LiteRT 0.15.0, and companion versions 0.0.18 / 0.0.10 remain unchanged.
• LiteRT v0.17 qualification remains separate. The existing grammar-repetition limitation remains tracked by Qualify post-v0.4.0 upstream grammar and GDN correctness fixes llamadart-native#76.
• Refreshed with a normal merge of canonical main; no rebasing or force push. Earlier head/base CI and audit evidence is superseded.
• Draft only. Mark-ready, merge, publication, tags, dispatch, settings, and runtime-pin changes require separate authorization. Merging this release-prep branch activates release automation.

Test Plan

Flutter 3.47.1 / Dart 3.13.1 on macOS; final candidate 3b84cb4ffb432e28f589324208dc7d1a69bf8d73.

• dart run tool/prepare_workspace.dart
• dart format --output=none --set-exit-if-changed .
• dart analyze
• dart test -p vm -j 1 --exclude-tags local-only (2055 passed, 77 skipped).
• dart test -p chrome --exclude-tags local-only (925 passed).
• Docs build and link validation.
• Release verifier default and strict mode; exact metadata regression command (24 passed).
• git diff --check.

Matrix Evidence

Matrix row	Scope	Platform/model/backend	Result	Evidence
release-metadata-verification	Core patch, snippets, companion pin guards	macOS; no model required	pass	dart run tool/testing/verify_release_docs_versions.dart --release-prep && dart test -p vm -j 1 test/unit/tooling/verify_release_docs_companion_pins_test.dart
high-risk-exact-head-independent-qa	Refreshed exact metadata diff	Fresh independent Astra-high auditor	pass	codex-adversarial-release494-refresh accepted exact head/base; independently passed strict metadata24 and readiness/classifier112 tests; zero P1 findings and unresolved threads

High-risk regression review

• Classification: high-risk / artifactConsumer; bounded release-metadata-verification route.
• Implementation task: release/0.8.24-prep refresh.
• Independent blocking QA task: fresh Astra-high codex-adversarial-release494-refresh, accepted exact head/base; independent from implementation.
• Exact head / current base: 3b84cb4 / dda9457.
• Production-branch deletion, bypass, or miswire proof: N/A to runtime code; bounded literal Git-blob metadata evaluator internally consistent.
• Affected-family real-model/artifact evidence: N/A; no implementation or pin changes.
• Known PR-caused P1 regressions: 0, independently reviewed.
• Unresolved review threads: 0, independently verified on the refreshed head.

Current CI

All 15 check contexts passed on 3b84cb4ffb432e28f589324208dc7d1a69bf8d73 against canonical main/base dda9457a1caf18e69696528d258af584d68d07fd: CI, LiteRT smoke, chat preview, and read-only advisory. Final live state: draft, MERGEABLE, CLEAN, zero unresolved review threads. Mark-ready and merge remain separate authorization boundaries.

The fresh repository-local evaluator confirms internally consistent evidence for this exact head/base and returns documented exit 2 / externalPrerequisitesUnavailable (unverifiedPrerequisites). External authenticated-auditor, publication, and ruleset prerequisites remain unavailable; this result does not assert operational readiness.

[github-actions]

Chat app preview deployed for 3b84cb4.

• App: https://leehack-llamadart-chat-pr-494.static.hf.space
• Space: https://huggingface.co/spaces/leehack/llamadart-chat-pr-494
• Repo: leehack/llamadart-chat-pr-494