feat(injected-helpers): extra fiber roots for portal modal support (closes #126 Gap B)

[Lykhoyda]

Summary

Closes Gap B of #126 — cdp_interact press testID="..." failing on fields inside react-native-actions-sheet modals (and other portal-mounted React subtrees) because their fiber roots are not in React DevTools' getFiberRoots() registry.

Gap A (TextField wrapper / RHF Controller) was shipped in #179 via cdp_interact action="setFieldValue".

What changed

1. Extracted private iterateAllRoots(cb) primitive in injected-helpers.ts. Owns the renderer-iteration logic that forEachRootFiber and findAllRootFibers were duplicating, plus the new extra-roots step.
2. Both public helpers became thin wrappers — same return shapes as before, zero caller changes.
3. New extractFiberFromInstance(inst) helper turns user-provided component instances into fibers via three accepted shapes: _reactInternals (modern React), _reactInternalFiber (legacy React), or already-a-fiber duck-type (escape hatch).
4. globalThis.__RN_AGENT_EXTRA_ROOTS__ is the user-facing opt-in: set it to a function returning component instances. Called fresh on every fiber-root scan.
5. Tool description + template snippet for discoverability.

Architecture

• One extension point for extra-roots (inside iterateAllRoots) — DRY across both wrappers.
• Per-resolver try/catch isolates user-side bugs from native renderer iteration.
• Synthetic rendererId: -1 marks extra-roots in the collector path.
• Failure modes match the silent convention of __NAV_REF__ and __ZUSTAND_STORES__ (no console warnings on misconfig).

Test plan

• 1527 / 1527 cdp-bridge unit tests passing (+12 net new in gh-126-extra-roots.test.js and +1 drift-guard in find-active-renderer-migration.test.js)
• extractFiberFromInstance covers all 3 input shapes + rejection cases (including dual-key duck-type rejecting generator-like objects with only .return)
• iterateAllRoots extra-roots step covers partial-failure, null-mixing, throwing resolver, non-array return, undefined resolver, sparse-array holes, non-function resolver (typeof guard discrimination)
• forEachRootFiber delegation preserves short-circuit through to extra-roots
• End-to-end: cdp_interact press testID against a component reachable ONLY via extra-roots fires its onPress (the user-visible fix)
• Pure refactor in Task 3 (extract iterateAllRoots) verified by full existing-suite pass with NO behavior change before Task 4 wired extra-roots
• CI green
• Deferred: Manual rehearsal on a real RN app with react-native-actions-sheet modal — not blocking merge per spec §11

Out of scope

• Auto-discovery via React DevTools onCommitFiberRoot (rejected in brainstorm — too deep into internals; opt-in is enough)
• getTree() default path (no filter) does NOT see extra-roots — deliberate, see spec §5
• /doctor probe for portal-library deps — rejected in brainstorm
• docs-site portal-roots page — rejected in brainstorm

Refs

• Spec: docs/superpowers/specs/2026-05-27-gh-126-gap-b-extra-roots-design.md (workspace repo)
• Plan: docs/superpowers/plans/2026-05-27-gh-126-gap-b-extra-roots.md (workspace repo)
• bug: dual CDP gap blocks Maestro automation through TextField wrappers and action-sheet portal modals #126 — Dual CDP gap (TextField wrappers + portal modals)
• feat(cdp-interact): setFieldValue action for React Hook Form fallback (closes #126 Gap A) #179 — Gap A (RHF Controller fallback)

🤖 Generated with Claude Code