Add root evidence artifact policy

[maniczko]

Summary

• Add root-level ignore rules for ad hoc visual/debug evidence.
• Document evidence artifact hygiene in docs/release-checklist.md.
• Remove tracked root screenshot rssmaster-sources-simplified-1440.png from the repository root.

Closes #15

Local artifact cleanup

Preserved the root evidence under ignored output before cleanup:

• output/manual-evidence/2026-05-25-root-artifact-cleanup/active-filter-chips-snapshot.md
• output/manual-evidence/2026-05-25-root-artifact-cleanup/active-filter-chips.png
• output/manual-evidence/2026-05-25-root-artifact-cleanup/rssmaster-sources-simplified-1440.png

Validation

• git status --short --branch in the issue worktree: clean after commit, branch ahead 1 before push.
• Root artifact scan in C:\Users\user\Desktop\RSSmaster: no matching root screenshot/snapshot/debug artifacts after move.
• git ls-files | Where-Object { $_ -match '^[^/]+\\.(png|jpg|jpeg|webp|gif)$' }: no tracked root image files after commit.
• git diff --check passed with CRLF warnings only.
• Docs review: docs/release-checklist.md now states evidence belongs under output/.

Tests not run

• npm run build was not run because this is docs/gitignore/artifact cleanup only and does not touch frontend code.

Risks

• output/ is ignored, so preserved local evidence is not portable through git; the PR documents the paths and intent.
• Root-level images are now ignored by default. Intentional long-lived assets should live under apps/web/public/, docs asset folders, or another explicit tracked path, not repo root.

[gemini-code-assist]

Code Review

This pull request updates the .gitignore file to exclude various image and markdown debug artifacts from the repository root and adds a new 'Evidence artifact hygiene' section to the release checklist documentation. The documentation changes provide guidelines for managing generated evidence within the output/ directory. A review comment suggested clarifying that since the output/ directory is ignored by Git, artifacts should be uploaded directly to pull requests or issues while referencing the local path for traceability.

[gemini-code-assist]

The instruction to "reference the output/... path" in a PR or issue body may be confusing for reviewers, as the output/ directory is ignored by Git and its contents are not available to others. It is recommended to explicitly advise uploading the artifact to the PR or issue comment directly, while mentioning the local path for traceability.

Suggested change

	- If evidence must be linked from a PR or issue, reference the `output/...` path in the PR body or issue comment instead of committing ad hoc root artifacts.
	- If evidence must be linked from a PR or issue, upload the artifact to the PR/issue comment and mention its `output/...` path for traceability instead of committing ad hoc root artifacts.