RELEASE @W-22462048@ Releasing v1.21.0

[nikhil-mittal-165]

No description provided.

[git2gus]

Git2Gus App is installed but the .git2gus/config.json doesn't have right values. You should add the required configuration.

[aruntyagiTutu]

Reviewed as a release rollup PR for v1.21.0. Walked through the consolidated diff against the rolled-up commits:

• SECURITY.md compliance upload: file already exists in the repo (verified via API); this commit is a pre-existing addition being carried into this release, nothing new to flag.
• ApexGuru insights/skip-notification feature (#W-22393677): new InsightsHandler cleanly separates the 'ApexGuru skipped' UX (org-not-connected / API-unavailable / unexpected-error) from the core run action, with sensible per-error-code display policy (NO_ORG_CONNECTION suppressed after first show per session, others always shown). CodeAnalyzer.scan()'s return type change from Violation[] to ScanResults is threaded consistently through CodeAnalyzerRunAction, extension.ts wiring, and all stubs/spies. Good test coverage across unit (insights-handler.test.ts), integration (insights-handler.integration.test.ts), and message-formatting (messages.test.ts) levels, including the 'old CLI with no insights field' backward-compatibility case.
• GUS info (#361) and dependency bumps (#W-22462041/#W-22462048): CODEOWNERS/package.json/package-lock.json changes are mechanical and consistent (vscode engine ^1.120.0→^1.125.0, esbuild/typescript-eslint/etc. minor bumps, matching lockfile regen).
• SHA256.md: updated hash/filename for the 1.20.0 vsix, consistent with the release process.

No unreviewed/surprise changes found. Approving.