factory: observe the first natural weekly slow run on develop

## Outcome

Prove one auditable natural weekly execution of the complete slow SDK-Rust
evidence line from protected default branch `develop` while reserved `main`
remains empty/minimal and protected.

## Selected mechanism

ADR 0120 selected GitHub's native schedule after moving the repository default
branch to protected `develop`. No personal token, GitHub App, external
scheduler, or `main` workflow shim is used. ADR 0127 retains one required Linux
`fast` pull-request gate and treats `slow` as production-promotion evidence.

The slow workflow records requested/actual revision, run attempt, event,
timestamps, conclusion, and artifact links; uses ephemeral read-only repository
credentials and bounded concurrency/timeouts; and is audited by the read-only
`scripts/factory slow-live` command.

## Completed evidence

- [x] Protected `develop` is the GitHub default branch; reserved `main` remains
independently protected.
- [x] Native weekly and manual slow triggers are active on `develop`.
- [x] Exact-SHA metadata, immutable receipt, bounded concurrency, retention,
failure visibility, and missed-run detection are enforced.
- [x] Credentials cannot publish crates or bypass branch protection.
- [x] Manual exact-merge run
[35006444994](https://github.com/hyperledger-identus/sdk-rust/actions/runs/35006444994)
passed the complete matrix at
`66ec2b9b3a7ec35cf21ecc52cdca5bebed0b4d0d` in 31m15s.
- [x] Existing documentation and workflow claims reflect native scheduled,
manual, and local evidence accurately.
- [x] Rollback affects only the scheduling/default-branch integration and does
not expand or weaken pull-request `fast`.

## Remaining acceptance

- [ ] Observe the first successful natural Monday `schedule` attempt (attempt
one, not a manual rerun) from protected `develop` and attach its exact
revision, conclusion, immutable receipt, and artifact links.
- [ ] For M3, run/attach the complete slow receipt on the unchanged frozen
release-candidate revision if it differs from that scheduled revision.

## Non-goals

- Running the slow matrix on every pull request or merge.
- Publishing, releasing, or populating `main`.
- Weakening the `develop` ruleset or required fast checks.
- Coupling SDK runtime crates to factory infrastructure.

## Relationships

- Implemented operationally by ADR 0120 and refined by ADR 0127.
- Final natural-run evidence is an M3 prerequisite tracked by #326.

Start with ADR 0120 and ADR 0127, then inspect the native weekly schedule on protected develop and run the read-only scripts/factory slow-live command. Observe the first successful natural Monday schedule attempt, not a manual rerun, and attach its exact revision, conclusion, immutable receipt, and artifact links. Confirm the complete slow receipt on the frozen release-candidate revision for M3 if it differs.

Written by the indexing model from the issue text.