[Task] Reconcile 3.8/3.9 release work and refresh consolidated upstream source tips

[sfmskywalker]

Program: #8194
Parent: #8197

Outcome

Carry all work from the 3.8.x and 3.9.0 release lines into main, and reconcile subsequent Elsa Studio and Extensions main changes into the consolidated Core source without losing newer Core changes.

Scope

• Audit stable 3.8.x/3.9.0 tags and release branches in Core, Studio and Extensions against their current main branches.
• Preserve release history through forward merges; document reviewed equivalent changes and release-only settings.
• Carry missing upstream changes into Core's established mapped paths, preserving Core adaptations and imported source history.
• Record pinned source tips and a disposition for every upstream changed path, including already-ported changes and inert legacy build assets.
• Refresh the program board to reflect the completed original import (Import Extensions and Studio histories into consolidated source #8409) and this catch-up lane.

Acceptance and verification

• All audited release refs are ancestors of their repository main, or any deliberately retained difference has explicit evidence and disposition.
• Core contains the reconciled upstream main tips as ancestors and every mapped functional delta is represented, with regression tests where upstream provides them.
• Focused affected tests and required current-head PR checks pass; final integration is reviewed before merging.
• Current 3.10 versioning, sole-publisher cutover policy and non-packable imported packages remain intact. No feed publication, release, deployment or repository archival is part of this task.

Baseline

Core main: 91a1c07232e806436c5e759086bbb9b0aee92234.
Studio main: efde64ef2b1a11ee8e6db9c4b13f2d313ffbe898.
Extensions main: 98a185a303b6c96347d25c780528ce37f2f864a3.
Original import #8409 merged 2026-09-29 at 8b34ab1e71c22c853e1aa340774231c80e92e677.

All implementation and verification uses isolated worktrees. Core integration branch: codex/consolidation-catchup.

[sfmskywalker]

Source reconciliation is accepted on main:

• Extensions Update ForEach.cs #285 and Dynamic ActivityProperty value  #286; current source main f237b64cfa368a119f653d44e555bda90581a5cf. Final hosted source build/test/pack: 537 passed, 0 failed, two existing provider skips.
• Studio Elsa 2.0 Mistake and a bug in guide #1061 and Can CompositeActivity be created using IActivityTypeProvider? #1125; current source main 3d028a4e9a3267b291f3d43d8064b5c81a6f2759. Final hosted source build/full tests: 1,911 passed, no failures/skips.

Core integration PR #8624 is now at 8d4df05ae90bb5e73bfe996c5f958cb0e4c4c63d. Both accepted source histories and all35 advertised 3.8/3.9 release refs are ancestors. Independent aggregate review approved this exact head after checking all48 Extensions and353 Studio path/mode/blob receipts, the163-asset legacy validator, and scoped regression evidence. Core hosted CI and required Greptile review are running; the task remains In Progress/In Review until those gates pass and the PR merges.

All implementation used worktrees. Existing release/publishing configuration is preserved, and source merge subjects suppressed automatic package publication. The broader program and publisher cutover remain separate.

[sfmskywalker]

Completed through Core #8624, preserving release and source history with merge commits.

• All 35 advertised 3.8.x/3.9.0 release branches and tags are verified ancestors of their repository main and consolidated Core main.
• Current accepted Studio and Extensions main commits are preserved in Core. Receipts account for every changed path: 353 Studio and 48 Extensions.
• Source delivery: Studio Elsa 2.0 Mistake and a bug in guide #1061/Can CompositeActivity be created using IActivityTypeProvider? #1125 and Extensions Update ForEach.cs #285/Dynamic ActivityProperty value  #286/Unable to have a custom activity with input as JavaScriptExpression<int?> #287. Final source CI: Studio 1,911 passed without skips; Extensions 539 passed with two unchanged provider skips.
• Final Core head: b43a17a9a95c2ddab09dd99d1f5eb420915e2608. Merge: 6dbfc58624c28e147a90e2d2b0d1a610817012e2. Exact-head independent review and Greptile 5/5 passed; all hosted CI completed successfully. Main Compile/Test: 7,616 passed, zero failed, 145 unchanged skips. Known skips match the earlier successful run.
• Legacy asset validation passed all 163 assets. Original checkout changes remain untouched; all implementation used worktrees.

Pinned source decisions and validation checkpoints are in doc/integration-program/release-catchup-verification.md and the adjacent machine-readable receipts. This completes the release catch-up task; broader program #8194 and parent #8197 remain open for their own acceptance criteria. Publisher cutover, feed publication, deployment and repository archival were not performed.

Remote main proof after merge:

• elsa-core: 6dbfc58624c28e147a90e2d2b0d1a610817012e2; 12 release refs verified.
• elsa-studio: 3d028a4e9a3267b291f3d43d8064b5c81a6f2759; 13 release refs verified.
• elsa-extensions: e189390b3ea10b730c4d66bf40e357f7621374ab; 10 release refs verified.

Final CI: Compile/Test, coverage and package construction.