Completes the deferred B8 half. `--context-window auto` now probes the
configured model and calibrates SKL/CML budgets to its real window instead
of always falling back to the conservative advisory anchor.
- lib/context-window.mjs: pure modelToContextWindow() maps known 1M-tier
model IDs (Fable 5, Opus 4.8/4.7/4.6, Sonnet 4.6 — verified June 2026 —
plus the explicit [1m] tier tag, dated/provider-prefixed IDs, and the
opus/sonnet/fable aliases) to the 1M window; unknown/unconfirmed -> null
(caller keeps the conservative anchor). resolveContextWindow() auto branch
now probes opts.model: recognized -> auto-probed (not advisory); unknown
or unpinned -> auto-unresolved (advisory, pre-B8b behavior).
- lib/active-model.mjs (new): resolveActiveModel() reads the model the way
Claude Code resolves it — shell ANTHROPIC_MODEL override, then settings
cascade local > project > user. Injectable env, hermetic under test HOME.
- scan-orchestrator: resolves the active model only when the flag is `auto`
and threads it into resolveContextWindow; posture inherits via runAllScanners.
Default (no flag) and explicit --context-window <n> paths ignore the model
and stay byte-stable; frozen v5.0.0 + SC-5 snapshots untouched. TDD: 17 new
tests (context-window mapping/probe + active-model cascade). Suite 1296 green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>