fix: align command prompts with active shell

[zhuowp]

Blocked on an official CodeWhale release; keep draft.

Commands submitted to the legacy Bash tool can contain Unix syntax even when the runtime selects PowerShell. Pin the shell-aware CodeWhale candidate and make application instructions follow the actual execution shell instead of prescribing Unix examples.

The engine change derives tool and command guidance from the existing dispatcher, covers Bash/sh/zsh/cmd/fish/custom paths, and leaves execution, permissions, tool names, and background semantics unchanged. The parent guard pins the review candidate explicitly; published r13 branches and tags are unchanged.

Dependency: Pinvou/CodeWhale#42 (candidate 0d409a97802179f1df9bcdbef185c1bfb5dc23e2). Upstream: Hmbown/Codewhale#5900.

Validation:

• CodeWhale library target compiled; 23 selected guidance tests passed.
• Application preview regression: 11/11; architecture guard and fork guard --fast passed.
• Initial four-task live-model comparison: Pro 3/20 to 20/20; Flash 2/20 to 19/20.
• Final curl-reminder ablation: both arms 19/20; zero shell mismatch errors. The final candidate removes that tool-level sentence. Application hints remained constant.
• Evaluation script compilation and offline paired-fixture/after-only checks passed.

These are focused Windows PowerShell 5.1 simulations, not full desktop or non-Windows runtime coverage. The exported catalog and standalone evaluation schemas differ in the documented anyOf sanitization. See docs/shell-guidance-evaluation.md for full methodology and limits.

Independent AI-assisted review accepted the scoped source changes. Integration review found that scripts/verify-public-submodule.sh still requires immutable r13, which differs from this candidate. An authorized Pinvou/CodeWhale maintainer must integrate #42 and publish a new immutable tag; then align the parent gitlink, verifier, guard, and docs to the actual release and rerun CI. zhuowp has no push permission to that official repository. The release verifier is intentionally not weakened and r13 is not moved. This PR stays draft until that dependency is resolved.