feat(cli): --revise-from-branch on foreman dispatch for in-place PR refresh

[joryirving]

What

Add --revise-from-branch <ref> to llmkube foreman dispatch. When set, the dispatched AgenticTask has both payload.branch and payload.reviseFromBranch stamped to that ref, so the executor restores the prior attempt and force-with-lease pushes an update to the same branch (and open PR) instead of cutting a new one.

Why

Post-PR iteration (a failing E2E, a reviewer request-changes) shouldn't require regenerating the whole branch — that wastes compute, tokens, and power for a one-line fix. The CRD field (payload.reviseFromBranch) and executor path already exist (#951, #978); today the only way to trigger them ad-hoc is hand-writing an AgenticTask. This flag makes incremental revision first-class for CLI-driven dogfooding.

Closes #996

How

• New dispatchOptions.reviseFromBranch field, bound to --revise-from-branch.
• New validateReviseFromBranch helper: when the flag is set, requires exactly one issue (a revision targets a single branch — matches the issue's "Notes").
• buildTask stamps Branch and ReviseFromBranch together from the flag on the revision path; both stay empty on the fresh-branch path.
• Help text gains a third example showing the revision flow.
• Tests added: TestBuildTask_ReviseFromBranch (table: unset+set), TestValidateReviseFromBranch (table: 5 cases), TestRunDispatch_ReviseFromBranchFiresBeforeFetch (asserts the rule fires before the GitHub fetch).

The executor (pkg/foreman/agent/executor_native.go) and the WorkloadReconciler (internal/foreman/controller/workload_iteration.go) already consume ReviseFromBranch; nothing under api/foreman/ or charts/ changes.

Checklist

• Tests added/updated
• make test passes locally
• make lint-all passes locally (darwin + linux)
• Commit messages follow conventional commits
• All commits are signed off (git commit -s) per DCO
• AI assistance (per CONTRIBUTING.md): code and PR description authored with assistance from an LLM-driven session in opencode (model: litellm-anthropic/MiniMax-M3). Design, commits, and verification all performed by the same session against the user's stated intent.
• Documentation updated (user-facing) — llmkube foreman dispatch --help example block shows the new flag.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[Defilan]

Nice flag, but there's a merge-order gotcha with #1042 that makes it a no-op as written. #1042 gated the reviseFromBranch restore behind BranchStrategy == rebase, and the default is now reset — so a dispatched task that sets ReviseFromBranch but not BranchStrategy falls through to the fresh-cut path and never restores the prior attempt.

buildTask needs to also stamp BranchStrategy: BranchStrategyRebase on the revision path. The unit test passes because it only checks payload stamping, not the executor behavior — worth asserting the strategy too so this can't regress. Fix that and it's good.