Add manifest update command

[heyitsaamir]

Summary

• Adds teams app manifest update for quick manifest edits without the download/edit/upload dance.
• Supports --set-json and --remove, with schema validation before anything gets uploaded.
• Adds a shared manifest update service so future commands can reuse the same flow instead of each one hand-rolling manifest writes.

How it works

• The command resolves the app + token, then delegates the real work to applyManifestUpdate() in src/apps/manifest-update.ts.
• The shared service downloads the current app package, reads manifest.json, applies the requested mutations, bumps the patch version once, validates the final manifest, uploads it, then verifies the changed paths survived TDP import/export.
• Schema validation uses the manifest $schema URL when present, or derives it from manifestVersion. Schemas are fetched only from Microsoft-hosted schema URLs and cached locally.
• --json mode stays non-interactive and returns structured errors/results. Mutating JSON mode requires --yes, unless it is a dry run.

Notes

• --set-json is intentionally the only set operation
• Post-upload verification catches cases where TDP accepts a schema-valid field but drops it during app-definition conversion.

Test plan

• npm run check-types
• npm run build
• npm run test -- manifest-mutate.test.ts manifest-update-command.test.ts manifest-schema-url-security.test.ts manifest-schema-validation.test.ts manifest-validation.test.ts
• npm run test

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