[codex] Release 0.4.1 findings fixes

[baskduf]

Summary

This patch release fixes two findings-ledger edge cases and prepares the codex-fable5 plugin metadata for 0.4.1.

Changes

• Bump codex-fable5 plugin version to 0.4.1 and update the stable README install ref.
• Add 0.4.1 changelog notes for the findings fixes.
• Archive stale findings.json when goals create --force replaces a plan, so old findings no longer block the new final checkpoint.
• Report controlled codex-fable5 JSON errors for malformed local ledgers instead of Python tracebacks.
• Add regression tests for forced plan replacement and malformed ledger JSON handling.

Validation

• python3 -m unittest discover -s tests -v passed: 21 tests OK.
• python3 -m py_compile ... passed for scripts and tests.
• sh -n passed for codex-fable5, codex-findings, and codex-goals wrappers.
• python3 plugins/codex-fable5/skills/codex-fable5/scripts/fable_coverage.py passed with 71 matrix rows.
• plugins/codex-fable5/bin/codex-fable5 findings gate passed.