[ArnauvGilotra]

Changes

• Upload only CantoIME-Setup.exe from a successful build.yml run for the release tag's exact commit.
• Trigger on release publication, including releases published from drafts. Wait up to ten minutes for a pending build; fail rather than substitute a different commit. Re-running replaces the same-named asset.
• Keep README short: installation, essential controls, options and limitations. Move build instructions, custom dictionary format and implementation details to BUILD.md.
• Audit both documents against current code, including cache-first loading, fallback parsing, settings application and build commands.
• Remove the mocked workflow test file as requested; workflow upload still needs real release verification.
• Correct stale README instructions: install the Chinese language first, then manually add the registered keyboard in Settings.

Verification

• actionlint passed for both workflows.
• Confirmed the existing Build API returns the expected commit and CantoIME-x64 artifact.
• Documentation links and diff whitespace checked.
• No live release was created and no release asset was uploaded during testing. The first publication after merge is the end-to-end verification.

Maintenance

Artifacts must still be retained by GitHub. If missing or expired, rerun Build for the tagged commit, then rerun the release workflow. Details are in BUILD.md.