[codex] Fix stale deferred rewrite state

[svarlamov]

Summary

Fix stale deferred rewrite state for operations that apply changes now and consume attribution on a later git commit.

• Add RED TestRepo regressions for abandoned cherry-pick --no-commit and abandoned merge --squash followed by an unrelated commit from the same base.
• Guard pending squash/no-commit cherry-pick consumption by requiring source added content to overlap the final commit's added content.
• Drop stale or base-mismatched pending state instead of reusing it for an unrelated commit.

Root Cause

merge --squash and cherry-pick --no-commit stored worktree-scoped pending state and later consumed it on git commit using only a weak base match. If the actual operation was abandoned without a traced daemon event, a later unrelated commit from that same base could inherit stale source session metadata.

Validation

RED checks before the fix:

• task test TEST_FILTER=test_cherry_pick_no_commit_abandon_does_not_affect_later_unrelated_commit NO_CAPTURE=true failed on stale cherry-pick session metadata.
• task test TEST_FILTER=test_abandoned_squash_merge_does_not_affect_later_unrelated_commit NO_CAPTURE=true failed on stale squash session metadata.

GREEN checks after the fix:

• task fmt
• task lint
• task test TEST_FILTER=test_cherry_pick_no_commit_abandon_does_not_affect_later_unrelated_commit NO_CAPTURE=true
• task test TEST_FILTER=test_abandoned_squash_merge_does_not_affect_later_unrelated_commit NO_CAPTURE=true
• task test TEST_FILTER=test_cherry_pick_no_commit_defers_to_final_commit_tree NO_CAPTURE=true
• task test TEST_FILTER=test_prepare_working_log_simple_squash NO_CAPTURE=true
• task test TEST_FILTER=cherry_pick:: NO_CAPTURE=true
• task test TEST_FILTER=squash_merge:: NO_CAPTURE=true
• task test