docs: concurrent execution of independent Forge Actions (NO_BUMP)

[pcvantol]

Owner-requested cross-product design

Companion to pcvantol/forge#134. Refines EP's existing Forge dependency-admission and P-QUEUE/multi-execution seams so independent Actions from one Mission can actually run concurrently, not merely become eligible.

Delivery

• Extend the owning dependency/admission contract: independent immutable submissions, target scope, actual overlapping delivery, isolated workspaces/providers/evidence, fenced leases, bounded capacity/fairness, same-operation recovery and incremental terminal readback.
• Add six PLANNED EP nodes and a documentary JSON DAG. Forge supplies contract fixtures; EP qualification does not depend on Forge's final integrated qualification, avoiding a cycle.
• Preserve true A+B artifact joins and allow A-only successors while unrelated B runs.
• Separate Actions from native subagents and retries; retain required candidate-bound assurance and correct multi-active timing/usage/export scope.

First profile: two authorized repositories on one compatible host. No full distributed fleet, Workspace UI, native nested-agent engine or complete SA programme prerequisite. Existing serial Mission 3, reset-development streams, #175 draft and delivered #271/#272 work remain untouched.

NO_BUMP documentation only: no runtime/schema/workflow/policy/grant/credential/installation/production-data or Mission change. Shared PA-01..PA-26 cases are future qualification requirements, not tests claimed already executed.

Validation at creation

Exact candidate CI and author-side documentary review pending. No locally rerun full product suite or installed concurrency proof claimed. Protected merge must use current applicable checks/reviews and expected head; no admin bypass or manufactured approval.

[pcvantol]

Author-side final documentary review on 0095c4e5c8033c3a547a328fdcb8a614794bd01b, companion Forge #134 now merged as b46aac196f64d018ae75f0d3492c841df9985ceb:

• Reviewed actual changed-file patch: existing producer-owned dependencies and EP-owned admission/resource/capacity boundaries retained, with explicit target/profile authorization, real execution overlap, per-invocation isolation and restart/failure/cancellation semantics.
• Independence is not inferred from Mission membership; same-Mission work has no blanket execution mutex. First profile isolates two repositories on one host. Real shared resources remain exclusive; same-repository parallel writers and native subagent engine are not implicitly enabled.
• A terminal A can unlock an A-only successor while B runs; a true A+B artifact join still waits. All required candidate-bound reviews remain, and sibling Actions cannot be presented as retries or hide unaccounted side effects before Mission completion.
• Local structural validation used exact fetched JSON bytes, matching remote blob hashes 0d511446414ac81f1d75939dfed5b7d0059b20bf (Forge) and 02ae60374a95d8a9f55800b774dde00bd6608992 (EP). All 13 nodes / 20 combined edges resolve and are acyclic; no Workspace dependency or cyclic final-qualification requirement.
• This is author-side design/JSON validation, not independent runtime assurance or execution of future PA-01..PA-26 tests. No runtime, schema, CI/protection, policy, version, credential, installation, CENTRAL reset or Mission-3 change.

Current exact-head CI has passed build/import, installed ingress, deterministic Genesis/Managed E2E and API contract steps; the remaining validation/coverage workflow is not yet terminal. Browser/localization jobs are skipped by the existing documentation profile, not claimed as executed UI qualification. Protected merge still waits for required checks.