FE-1125: Reconcile executor run driver

[kostandinang]

Summary

• Adds execute_orchestrate: drives a run end-to-end (created → run-local promotion_prepared) instead of calling each execute_* step by hand.
• src/executor/orchestrate.ts — a pure RunScheduler (linearScheduler) plus a generic drive() loop; run.json status is the loop state, and per-slice readiness comes from completion facts.
• Halts without advancing if a step cannot execute. Host promotion stays off the driven chain (separate accepted surface).
• ready() returns a set (length-1 today) so a future PetriScheduler drops in without reshaping the loop (D102-L).
• Clarifies the AgentRunnerPort fail-closed message so a launch without subagent deps is diagnosable, not mistaken for an unbuilt feature (surfaced during driver testing).

Verification

• npm run verify

[cursor]

PR Summary

Medium Risk
New orchestration path composes many lifecycle steps and injected ports in one call; tests use fake ports and assert parity/halt semantics, but real LLM+git E2E is still unexercised per plan notes.

Overview
Adds end-to-end executor run driving so a cook run can advance from created through run-local promotion_prepared in one CODE-mode call instead of stepping each execute_* tool manually.

Core: src/executor/orchestrate.ts introduces a pure RunScheduler (linearScheduler) whose ready() returns a set of next steps (length 1 today) from run.json status and slice completion facts, plus drive() that loops those steps through existing lifecycle functions and injected ExecutionPorts. Failed steps halt without advancing metadata; host promotion stays off the driven chain.

Product surface: New execute_orchestrate Pi tool (registered in execute mode, wired in app extensions) calls drive() with model/runtime context for agent slices. D102-L is added to SPEC; PLAN/topology docs mark the orchestrate-loop frontier as built.

Tests: Parity vs hand-cranked lifecycle, halt on port failures, scheduler contract, and once-per-slice runner invocation. AgentRunnerPort missing-deps error text is clarified (no behavior change).

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[kostandinang]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• FE-1125: Reconcile executor run driver #285 👈 (View in Graphite)
• FE-1118: Reconcile host executor promotion #282 : 1 other dependent PR (#284 )
• FE-1112: Reconcile run-local executor promotion #279
• FE-1111: Reconcile executor agent runner #278
• FE-1109: Reconcile executor sandbox worktrees and test runner ports #275
• FE-1089: Reconcile executor with alpha branch #274
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