feat(domain): add git rebase-on-main with agent-powered conflict resolution and sync-main

[arielshad]

Summary

• Rebase feature on main — adds rebaseOnMain() to IGitPrService that rebases a feature branch onto origin/<baseBranch> with automatic agent-powered conflict resolution. Before rebasing, the system syncs the remote-tracking ref and verifies the worktree is clean. When conflicts are detected, an AI agent iteratively resolves them (up to 3 retries per commit), validates no conflict markers remain, stages resolved files, and continues the rebase. Falls back to git rebase --abort if the agent cannot resolve.
• Sync main with remote — adds syncMain() to IGitPrService that fetches the latest remote state. Works from any branch: uses git fetch origin <baseBranch> when on a feature branch (updates only origin/<baseBranch>, avoids touching the local branch ref), or git pull --ff-only when on the base branch. This design prevents the "refusing to fetch into branch checked out at..." error when main is checked out in another worktree.
• New error codes — extends GitPrErrorCode enum with REBASE_CONFLICT and SYNC_FAILED for precise programmatic error handling.
• Use cases — adds RebaseFeatureOnMainUseCase (resolves feature, worktree path, invokes sync + rebase with conflict resolution) and SyncRepositoryMainUseCase (resolves repository, invokes sync).
• Agent-powered conflict resolution — ConflictResolutionService orchestrates agentic resolution via IAgentExecutorProvider: detects conflicted files, invokes AI agent with conflict context (file contents, branch info, markers), validates resolution, retries up to 3 times per commit, aborts on exhaustion.
• Web UI support — adds server actions (rebaseFeature, syncRepository), action hooks, and UI buttons. Feature drawer overview tab shows a "Rebase on Main" button under a BRANCH SYNC section. Repository drawer shows a "Sync Main" button under GIT OPERATIONS. Both actions delegate to existing use cases via DI.
• Feature flag gated — all git rebase & sync UI is hidden behind the gitRebaseSync feature flag, configurable from the Settings page.
• Full spec lifecycle — includes spec analysis, requirements, research with technology decisions, implementation plan, task breakdown, and implementation across all four architecture layers (domain, application, infrastructure, presentation).

Key Fix (Iteration 4)

The syncMain method previously used git fetch origin main:main which fails with fatal: refusing to fetch into branch 'refs/heads/main' checked out at '/path/to/repo' when the main branch is checked out in the primary worktree. Now uses git fetch origin main (updates only the remote-tracking ref origin/main) and rebaseOnMain targets origin/<baseBranch> directly. This correctly supports git worktree workflows where the main branch is checked out in the primary repo.

Evidence

Feature Flag in Settings

Repository Drawer — Sync Main

Feature Drawer — Branch Sync Status & Rebase on Main

Behind (with Rebase button)	Up to Date	Rebasing	Rebase Error

Overview Tab with Rebase Action

Loading State

Test Evidence

• Unit tests — 63 tests passing across 5 feature-specific test files: GitPrService rebase/sync (34), ConflictResolutionService (6), conflict resolution prompt builder (10), RebaseFeatureOnMainUseCase (9), SyncRepositoryMainUseCase (4)
• Integration tests — 16 tests passing against real temporary git repos: syncMain (6, including worktree-safe fetch and diverged-from-feature-branch), rebaseOnMain (7), helper methods (3)
• Full test suite — 318 unit test files (4082 tests), 42 integration test files (500 tests), zero regressions
• Validation — lint, format, typecheck, TypeSpec compilation all pass
• Build — compiles without errors

Test plan

• Unit tests for GitPrService.rebaseOnMain: clean rebase, conflict detection, dirty worktree rejection, rebases onto origin/main
• Unit tests for GitPrService.syncMain: fetch from feature branch (worktree-safe), pull from main, diverged rejection, error classification
• Unit tests for ConflictResolutionService: successful resolution, retry logic, abort on max retries
• Unit tests for RebaseFeatureOnMainUseCase: happy path, feature not found, sync failure, conflict resolution flow
• Unit tests for SyncRepositoryMainUseCase: happy path, repo not found, sync failure propagation
• Integration tests: syncMain succeeds from feature branch even when local main diverged (new test), rebase uses origin/main
• Web UI: server actions, hooks, and action buttons for rebase and sync wired correctly
• Storybook stories updated for BranchSyncStatus (all states), OverviewTab (rebase with sync), RepositoryDrawer (with git operations)
• All existing unit and integration tests continue to pass (no regressions)
• Build compiles without errors
• Lint passes with zero warnings

🤖 Generated with Claude Code

[github-actions]

Dev Release Published

Artifact	Version	Install
npm	1.123.0-pr396.f99e785	npm install -g @shepai/cli@1.123.0-pr396.f99e785

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_{Published from commit cf9bf25 | View CI}

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Dev Release Published

Artifact	Version	Install
npm	1.123.0-pr396.ac74a97	npm install -g @shepai/cli@1.123.0-pr396.ac74a97

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_{Published from commit 4d9ad80 | View CI}

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Dev Release Published

Artifact	Version	Install
npm	1.123.0-pr396.072b95e	npm install -g @shepai/cli@1.123.0-pr396.072b95e

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_{Published from commit abe495f | View CI}

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npm	1.124.0-pr396.2dd2ae6	npm install -g @shepai/cli@1.124.0-pr396.2dd2ae6

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npm	1.129.2-pr396.29a046b	npm install -g @shepai/cli@1.129.2-pr396.29a046b

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npm	1.129.3-pr396.d3c115b	npm install -g @shepai/cli@1.129.3-pr396.d3c115b

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npm	1.129.4-pr396.5d604d5	npm install -g @shepai/cli@1.129.4-pr396.5d604d5

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Artifact	Version	Install
npm	1.130.1-pr396.844e95f	npm install -g @shepai/cli@1.130.1-pr396.844e95f

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Dev Release Published

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npm	1.134.1-pr396.fe65c43	npm install -g @shepai/cli@1.134.1-pr396.fe65c43

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_{Published from commit 5107a96 | View CI}

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Dev Release Published

Artifact	Version	Install
npm	1.136.0-pr396.3419613	npm install -g @shepai/cli@1.136.0-pr396.3419613

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_{Published from commit 53b6247 | View CI}