docs(site): name context_for_task in the Map card, as experimental

[atlas-from-plumb]

The site already counted context_for_task in "Sixty structured tools" and in the Map ×9 card (since #629), but never named it.

Change (site/index.html, one line in the Map card):

• adds context_for_task to the card's tool list, starred like the other Plumb-specific tools;
• adds one sentence, marked experimental, on what the pack carries. Each part maps to an entry in CHANGELOG.md 0.24.1 (unreleased):
  • "starts from the files or symbols an agent names… one bounded pack": context_for_task, an experimental seeds-first context tool (feat(tools): context_for_task, a seeds-first bounded context pack (experimental) #629);
  • "their code, callers and related declarations": the same entry's Bodies and Neighbourhood items;
  • "the tests that reach them": names the tests that run your seed (feat(context): name the tests a call edge reaches, as a ready run_task filter #647);
  • "whether a Go caller list is complete": says when a seed's callers are complete (feat(context_for_task): say when a seed's callers are complete (per-call resolver outcome, schema 8) #648, fix(topology): read dot-importing files once per census, not per call site (6-10 s packs -> 0.2-0.4 s) #651);
  • "a note while the index is still being built": says when its index is still on its first pass (fix(context_for_task): say when the index is still on its first pass (PLAN-547) #668).

Counts: unchanged and still consistent. The groups sum to 60 (4+8+13+9+9+9+4+4), and Map ×9 matches the nine tools under docs/tools.md § Topology.

CHANGELOG: no entry. Earlier site edits rode with feature or release commits and had no separate entry, and the CHANGELOG describes the product, not the site.

No performance or cost claims.

🤖 Generated with Claude Code

[golimpio]

Approved on 5e7510f: independent subagent review PASS (fix re-reviewed PASS), CI 9/9 green, make verify-full-container EXIT=0 on this head. Site-only change; claims checked against CHANGELOG 0.24.1.