docs(#12863): add remote manifest residual headers

[lalalune]

Summary

• Add purpose headers to residual plugin-remote-manifest test files and example workers.
• Cover host shim, worker runtime, sub-agent, store/signature/permission tests, and install examples.
• Keep the patch comment-only; code tokens are unchanged.

Fixes #12863

Validation

• PASS bun run check:comment-only
• PASS bun run --cwd packages/plugin-remote-manifest test (139 tests)
• PASS bun run --cwd packages/plugin-remote-manifest typecheck
• PASS bun run --cwd packages/plugin-remote-manifest lint
• PASS git diff --check origin/develop...HEAD

Verification notes

• bun run verify was attempted after fix: green verify baseline — browser redact export, logger arg order, prober contract, biome drift #12919 landed. In this local sparse checkout, packages/scripts is not materialized (git sparse-checkout list only includes packages/core, packages/scenario-runner, packages/shared, plugins/plugin-computeruse, plugins/plugin-vision), so multiple package builds failed to resolve packages/scripts/rm-path-recursive.mjs and packages/scripts/with-package-build-lock.mjs; verify then exited 139. This is a workspace checkout limitation, not a code-token change in this PR.

Evidence

• UI/video/domain artifacts: N/A - comments-only change, zero functional diff machine-checked by scripts/assert-comment-only-diff.mjs.

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✨ Finishing Touches

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• Commit unit tests in branch docs/comments-b02d-remote-manifest

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[lalalune]

Local validation pass from isolated checkout /tmp/eliza-pr-12927.

Commands run:

node scripts/assert-comment-only-diff.mjs github-develop
git diff --check github-develop...HEAD
bun run --cwd packages/plugin-remote-manifest test
bun run --cwd packages/plugin-remote-manifest typecheck
bun run --cwd packages/plugin-remote-manifest lint

Results: all passed. Comment-only proof covered 25 source files; package tests passed 139 tests / 1432 assertions; typecheck and Biome lint were clean.

[claude]

Claude encountered an error —— View job

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