core: filter status compressible ranges via billion-context-kit viableRanges

[ranxianglei]

First (minimal) adoption of billion-context-kit — the new host-agnostic layer shared by the omp and pi adapters.

What

packages/core/src/status-tool.ts listed nudge.compressibleRanges unfiltered. Fragmented ranges (<200 tokens) cannot carry a meaningful >=50-char summary, and the kernel validates compress batches atomically — one tiny range in a model-followed batch rejects the whole call. Observed live on the omp adapter: a 14-range recommendation containing a 16-token range → every batch attempt failed with "Summary too short".

This wires the shared viableRanges filter (200-token floor, same constant the other adapters use) onto the status recommendation surface.

Scope (deliberately minimal)

• Only the filter — kernel stays at 0.0.19, no panel/delegation changes. viableRanges is dependency-free, so the kit's own acp-kernel pin does not affect this package's resolution semantics.
• Larger kit adoption (shared buildStatusPanel, topicFallback, prompt/tool surface) can follow once this repo stabilizes — the kit is the intended shared home for that surface.

Verification

• npm run typecheck --workspaces clean; npm test 54/54 pass (pre-existing suite, node --test).