Pull project docs URL into triage context

Per-project context/repo/docs are injected into the triage prompt and exposed via the tesks_project_context MCP tool, and the project's github_repo is now merged into the GitHub code-search scope.

The docs_url is currently only passed as a link — NOT fetched or summarized. Wire a fetch+summarize step so docs content actually informs triage:

• fetch the docs URL (timeout, size cap, respect robots.txt)
• summarize / extract relevant sections into CodeContextProvider-style snippets
• cache (5 min like code search) and feed into the triage prompt

--- Activation prerequisite --- The GitHub code-search path (and therefore the per-project repo scoping added in 8705607) is dormant until a token is configured. To turn it on:

• add GITHUB_TOKEN (a PAT with repo:read) to the development/tesks-secrets Secret (key GITHUB_TOKEN; optionally GITHUB_REPOS as a comma-separated fallback list)
• restart the tesks deployment (kubectl -n development rollout restart deploy/tesks) Then triage searches the configured repos PLUS every project's github_repo automatically. The same token is what the docs-fetch step should reuse.

Follow-up to the project-context feature (V5/V6).