cow: carry the live twap and composable keeper fixes into the port

[mfw78]

Carry the still-live TWAP and composable keeper correctness fixes onto the ported keeper.

Goal

Land the outstanding TWAP and composable keeper correctness fixes on the ported keeper: deduplication and retry classification, gate-marker leaks, revert-selector loops, the signature-race retry, and conditional-order removal, plus reconcile the grant deliverable divergence so the shipped keeper matches what was promised.

Scope

These are known-live correctness bugs in the current TWAP and composable keepers that must not be lost when the keeper is ported onto the generic venue seam. The work covers the retry and deduplication paths, leaked gate markers, tight loops on revert selectors, the race between signing and submission, and removal of stale conditional orders. Alongside the code fixes, it reconciles where the delivered behaviour diverged from the grant deliverable so the ported keeper is both correct and accountable to what was committed.

Milestone: M4: CoW on the generic seam (the shepherd bundle).

[mfw78]

Closing as already delivered, verified against origin/dev/m1@aec462a rather than taken on the issue text.

All six sub-issues are now satisfied on the tree. Closed already: #320 (shipped 9cac7c3 "twap: grant one next-block retry before dropping on InvalidEip1271Signature (#473)"), #54 (shipped 5270aa2 "twap-monitor: index ComposableCoW v2 ConditionalOrderRemoved (#472)"), #64 (shipped d88dc99 "docs: note the grant-M2 contract-mods divergence in milestone reporting (#465)"). The three still marked OPEN are all done on the tree too - see the per-issue findings for #121, #75 and #48 below. Nothing in the epic's stated scope (dedup+retry classification, gate-marker leaks, revert-selector loops, signature race, conditional-order removal, grant divergence) is outstanding.

Closed manually because the M-train merges into the non-default dev/m1 branch, so nothing auto-closes.