docs: publish Sourcey-generated llms index

[epistemedeus]

Description

Publishes an agent-readable llms.txt at the site root and keeps it reproducible from OpenScan's existing Markdown documentation. The checked-in index is generated with Sourcey 3.6.5 from seven real project guides pinned at commit 8ccaa3283333eb4616efe3255398a77ca6d6ef93.

Related Issue

Fixes #388

Type of Change

• Bug fix
• New feature
• Documentation update
• Refactoring
• Performance improvement
• Other (please describe):

Changes Made

• Add public/llms.txt, which Vite publishes at /llms.txt in production and PR previews.
• Add a Sourcey manifest covering the project overview, contributor guide, architecture, testing, workflow, and code-style sources.
• Add npm run docs:llms for deterministic regeneration with Sourcey 3.6.5.
• Pin every linked Markdown target to one project commit and fail regeneration if a source drifts without updating the pin.

Screenshots (if applicable)

Not applicable; this adds a machine-readable text endpoint.

Checklist

• I have run npm run format:fix and npm run lint:fix
• I have run npm run typecheck with no errors
• I have run tests with npm run test:run
• I have tested my changes locally
• I have updated documentation if needed
• My code follows the project's architecture patterns

Additional Notes

• npm run test:run: 105 tests passed.
• npm run build: passed, and dist/llms.txt is byte-identical to public/llms.txt (sha256:60d6a28bc1ba91068190eea7bbd41fab66770c7ececcb305b86ee58532a592c6).
• All seven pinned Markdown targets return HTTP 200, and two consecutive generation runs produced the same hash.
• The repository-wide npm run check currently reports eight pre-existing Biome errors in unrelated src/ files; the current Biome include rules do not process the added generator/config/text paths.
• npm run typecheck cannot currently start because the repository does not expose a tsc binary after dependency installation. This change adds no application TypeScript.