feat(stack): port replay HTTP upload + orchestrator to Rust

[jd]

Completes the replay-for-revision pipeline: the git-only half
landed in the previous commit (compute_merged_tree +
compute_tree_delta); this adds the GitHub Git Data API upload
that materialises the synthetic commit the revision-history
compare URL anchors at.

• upload_replay_commit — POST /git/trees with the delta,
  then POST /git/commits with parents=[old_sha] so
  compare/<old_sha>...<commit> shows just the amendment.
  Any API error coerces to None (matches Python's
  except httpx.HTTPError, ValueError); the failure is non-
  fatal because the revision-history row already carries a
  durable (raw) fallback URL.
• replay_for_revision — top-level orchestrator wiring
  compute_merged_tree → rev-parse parent_old^{tree} →
  compute_tree_delta → upload_replay_commit. Returns None
  on conflict, missing parents, empty diff (rebase fully
  absorbed the edit), git error, or API error so callers
  fall back to the plain old…new three-dot URL.

Coverage: 4 wiremock tests pinning the two-call shape, the
short-circuit on tree-POST failure, the short-circuit on
commit-POST failure, an end-to-end run against a real repo,
and the empty-diff short-circuit (no HTTP calls).

Co-Authored-By: Claude Opus 4.7 noreply@anthropic.com

Depends-On: #1536

[jd]

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	feat(stack): port detect_change_type + patch-id helpers to Rust	#1532
2	feat(stack): port StackComment renderer to Rust	#1533
3	feat(stack): port replay git helpers (merge-tree + diff-tree) to Rust	#1534
4	feat(stack): port RevisionHistoryComment to Rust	#1535
5	feat(stack): port stack push approvals decision to Rust	#1536
6	feat(stack): port replay HTTP upload + orchestrator to Rust	#1537	👈
7	feat(stack): port stack push git plumbing (notes fetch + push) to Rust	#1539
8	feat(stack): port stack push rebase log lines to Rust	#1540
9	feat(stack): port format_pull_description + build_change_tasks to Rust	#1541
10	feat(stack): port create_or_update_pr + orphan branch delete to Rust	#1542
11	feat(stack): port per-PR stack + revision-history comment upserters to Rust	#1543
12	feat(stack): port stack push planner (get_changes) to Rust	#1544
13	feat(stack): port stack push orchestrator to Rust	#1545
14	feat(rust): wire native stack push + delete Python push.py	#1546
15	chore: delete Python tree + simplify wheel/CI for pure-Rust binary	#1547

[mergify]

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🔴 ⛓️ Depends-On Requirements

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• depends-on=Mergifyio/mergify-cli#1532 [⛓️ feat(stack): port detect_change_type + patch-id helpers to Rust #1532 [stack]]
• depends-on=Mergifyio/mergify-cli#1533 [⛓️ feat(stack): port StackComment renderer to Rust #1533 [stack]]
• depends-on=Mergifyio/mergify-cli#1534 [⛓️ feat(stack): port replay git helpers (merge-tree + diff-tree) to Rust #1534 [stack]]
• depends-on=Mergifyio/mergify-cli#1535 [⛓️ feat(stack): port RevisionHistoryComment to Rust #1535 [stack]]
• depends-on=Mergifyio/mergify-cli#1536 [⛓️ feat(stack): port stack push approvals decision to Rust #1536 [stack]]

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• depends-on=Mergifyio/mergify-cli#1532 [⛓️ feat(stack): port detect_change_type + patch-id helpers to Rust #1532 [stack]]
• depends-on=Mergifyio/mergify-cli#1533 [⛓️ feat(stack): port StackComment renderer to Rust #1533 [stack]]
• depends-on=Mergifyio/mergify-cli#1534 [⛓️ feat(stack): port replay git helpers (merge-tree + diff-tree) to Rust #1534 [stack]]
• depends-on=Mergifyio/mergify-cli#1535 [⛓️ feat(stack): port RevisionHistoryComment to Rust #1535 [stack]]
• depends-on=Mergifyio/mergify-cli#1536 [⛓️ feat(stack): port stack push approvals decision to Rust #1536 [stack]]

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