[Docs] Evaluate walgit for repository bootstrap

[roomote-roomote]

​Opened on behalf of @mrubens. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

What changed

Added a technical evaluation of walgit as a possible repository bootstrap accelerator for disposable Roomote sandboxes. It documents the current clone/startup path, fit and non-fit, security and tenant-isolation constraints, and a gated A/B experiment with statistical success criteria.

The recommendation is a no-go for production adoption and only a conditional go for an isolated blobless bundle-uri experiment after existing setup telemetry proves clone transfer is a material bottleneck.

Why this change was made

The radar signal identified walgit's object-store-backed Git architecture as potentially useful for large repositories. A complete audit of 128 open PRs found no exact walgit, bundle-URI, mirror, or shared Git object-cache work; PR #934 is adjacent clone-timeout work and remains separate.

The evaluation turns that signal into a durable, source-pinned decision while avoiding a speculative provider or clone-path implementation. It also captures walgit's documented filtered-bundle caveat and current repository-authorization gap before either can become a production risk.

Impact

There is no runtime behavior change. Reviewers gain a concrete decision gate and experiment design that preserves the existing source-control provider as origin, fetch target, credential authority, and push destination.

[roomote-community]

1 issue outstanding. See task

• docs/technical-evaluations/walgit-repository-bootstrap.md:40 Existing setup-phase events do not record clone, fetch, or checkout/reset timing, so the proposed entry gate cannot be measured from current telemetry.

_{Reviewed 7cf2410}

[roomote-community]

Existing telemetry does not emit these stage-level durations. recordPhase reaches setup, which records initializeRepositories as one phase, but initializeRepositories and createWorkspaceManager do not pass that recorder into their nested timedStep calls; WorkspaceManager.timed therefore only writes debug logs for clone, fetch, and checkout. The stated entry gate cannot be calculated from existing setup events, so make stage-level event instrumentation a prerequisite rather than claiming this experiment needs no code change.