Add Opera cache cleaner extension baseline

opera-cache-cleaner-extension/docs/agent-handoff.md

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+# Agent Handoff
+
+## Current State
+
+The Codex repository baseline has been applied to the local Opera Cache Cleaner extension.
+
+## Notes For Next Agent
+
+- The project is not currently a Git repository in this workspace.
+- Expected Gitea repository: `https://git.wilkensxl.de/Toxic/Opera-Extensions.git`.
+- The project has no package manager and no external dependencies.
+- Use syntax checks and manual Opera extension testing as the main verification path.
+
+## Open Items
+
+- Initialize or connect a Git repository if the project should be pushed to Gitea.
+- Confirm whether this extension should live at the repository root or inside `opera-cache-cleaner-extension/` before enabling package publishing or Gitea API polling.

opera-cache-cleaner-extension/docs/release-checklist.md

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+# Release Checklist
+
+## Version
+
+- [ ] Version number updated in `manifest.json`.
+- [ ] `CHANGELOG.md` updated.
+- [ ] README checked for current installation and usage instructions.
+
+## Quality
+
+- [ ] Working tree is clean.
+- [ ] `node --check background.js` passes.
+- [ ] `node --check popup/popup.js` passes.
+- [ ] Manual unpacked-extension smoke test in Opera passes.
+
+## Security
+
+- [ ] `docs/security-review.md` is current.
+- [ ] No new permissions were added without review.
+- [ ] No secrets are committed.
+- [ ] Release artifact does not contain local config files.
+
+## Artifacts
+
+- [ ] `dist/opera-cache-cleaner-extension.zip` exists.
+- [ ] Zip contains `manifest.json`, `background.js`, `popup/`, and `icons/`.
+- [ ] Zip does not contain `dist/`, `.git/`, `.codex/`, `.gitea/`, or docs-only files.
+
+## Release
+
+- [ ] Git tag created.
+- [ ] Release notes written.
+- [ ] Release published.
+- [ ] Post-release download smoke test completed.

opera-cache-cleaner-extension/docs/security-review.md

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+# Security Review
+
+## Scope
+
+Project:
+
+```text
+Opera Cache Cleaner
+```
+
+Reviewed version or commit:
+
+```text
+1.0.0 local workspace
+```
+
+## Code Patterns Checked
+
+- [x] No `eval`.
+- [x] No dynamic `Function` constructor.
+- [x] No unsafe HTML injection found in the reviewed code.
+- [x] No shell execution.
+- [x] No external network calls.
+- [x] No secrets committed in the current source files.
+- [x] No unsafe file writes. Browser data changes are limited to cache removal.
+
+## Dependency Review
+
+Command:
+
+```bash
+No dependency audit command exists because the project has no package manifest or external dependencies.
+```
+
+Result:
+
+```text
+Not applicable.
+```
+
+## Runtime Review
+
+- [x] Manifest uses least-privilege permissions for the current feature set.
+- [x] No host permissions are declared.
+- [x] Local storage is used only for selected range, timer settings, and last run timestamp.
+- [x] Cache clearing uses `chrome.browsingData.remove({ since }, { cache: true })`.
+
+## Release Notes
+
+Known residual risks:
+
+```text
+No automated browser-extension integration tests exist. Perform an unpacked-extension smoke test in Opera before release.
+```