cli: Remove unreachable recovery and search paths

[BenWestgate]

Historical stack note: GitHub marked this PR merged when its head became an ancestor of #80 during the budget-preserving stack reorder. #105 restores the same patch-identical cleanup as a focused PR directly after #57. Review/integrate #105, not this historical boundary.

Refs #46 and #81.

What

After the earlier CLI cleanup, remove the remaining provably dead recovery and correction paths:

• Recovery passes the share list directly after all(isinstance(..., Share)) has already rejected every other type. The comprehension filter could never remove an item.
• _correction_plan returns only target lengths. Its primary set was always those same targets; its reduced set was always empty; its timed flag was always true. _search_many never read its reduced argument. Update the private callers, tests, and benchmark accordingly.

This is two atomic commits and 17 fewer production/test/tool lines. Correction scheduling, capture accounting, wallet calls, and public input validation are unchanged. The wrong-type guard flagged by mypy in bip93._bounded_artifacts remains because malformed runtime inputs can reach that public API.

Verification

• CLI and correction tests: 303 passed normally and 303 under python -O.
• Frozen differential correction verifier: 57 cases passed.
• Strict mypy, Ruff check/format, unused-argument check, installed source-size test, and git diff --check: pass.

Stacked directly on #80 so the review diff contains only this cleanup. The two stable patch-ids are unchanged from the previously reviewed #81-based head. Moving this cleanup ahead of #81 reduces the installed source to 5,188 logical lines and keeps every later intermediate tip under the authorized <5200 gate. Human integration order is #42 → #57 → #80 → this PR → #81 → #95. AI assistance and agent commit authorship are disclosed; responsible-human rewrite or squash is required by repository policy before integration.

[BenWestgate]

@codex review

[BenWestgate]

AI-assisted review performed at the maintainer's request and disclosed per docs/developer/AI_POLICY.md.

No correctness findings. The cast(list[Share], artifacts) follows an immediately preceding all-Share runtime check, so it removes an unreachable filter without weakening validation. _correction_plan() only returned targets plus values mechanically derived from those targets (primary == frozenset(targets), empty reduced, constant timed flag); _search_many() did not consume reduced. The cleanup therefore preserves search planning while removing dead state. Local focused run: 302 passed; the sole failure was the disposable checkout lacking the installed /usr/local/bin/codex32 entry point. Exact-head GitHub CI is green. Ready for human review/rewrite-squash under repository policy.