Factory: reconcile live backlog ownership and semantic freshness

## Outcome

Make the canonical SSI roadmap safe for continuous agent selection by reconciling its active issue ownership with live GitHub state and adding an explicit supervisor-facing freshness audit.

## Current evidence

At `develop@523c64d4ff71d97f71c44b55c99594f065896b56`, the offline backlog checker passes all 30 rows but two `in_progress` rows point to closed delivery children: IDR-004 -> #95 and IDR-023 -> #250. The native-binding issue #222 also lacks the final merged Android receipt from PR #231. Structural validity therefore does not prove operational backlog freshness.

## Scope

- Update active roadmap ownership to durable open component epics or a new focused child where implementation is actually active.
- Reconcile completed native DID binding evidence and close or narrow #222/#163 without activating publication or support claims.
- Add a network-explicit factory audit that compares delivery state with live GitHub issue state and fails when `in_progress` ownership is closed or unavailable.
- Keep the existing offline checker deterministic and network-free for fast CI.
- Document how the Desktop supervisor uses the live audit before selecting Pi work.
- Fix the observed Nix `stdenv.isDarwin` deprecation if it is isolated and behavior-neutral.

## Non-scope

No new SSI behavior, repository settings, release/publication, support activation, consumer mutation, or automatic issue closure. The audit reports drift; it does not mutate GitHub.

## Acceptance

- [ ] OpenSpec contract, research, constraints, design, and tasks pass factory readiness.
- [ ] Every `in_progress` backlog row references an open durable owner.
- [ ] A bounded live audit has deterministic tests for open, closed, unavailable, malformed, and rate/error outcomes without requiring network in CI.
- [ ] `scripts/factory` documents and exposes the explicit live audit path.
- [ ] #222/#163 receive truthful completion/remaining-scope receipts.
- [ ] Factory, focused tests, formatting, lint, and applicable Nix gates pass.

## Decision and rollback

This is routine, reversible repository-local factory maintenance under ADRs 0003/0004. The live audit remains opt-in supervisor evidence and can be removed without changing SDK runtime or public APIs.

Start by reading the existing offline backlog checker and the scripts/factory entry points, then review ADRs 0003/0004 and the referenced issue state. Define the opt-in live audit around deterministic tests for open, closed, unavailable, malformed, and rate/error outcomes. Done means active ownership is reconciled, native-binding receipts are truthful, supervisor usage is documented, and the listed factory, Rust, formatting, lint, and Nix gates pass.

Written by the indexing model from the issue text.