E0308 next-wave RCA worksheet — stratify current Rust residual into implementation-ready subfamilies; no broad E0308 fixes

[briansrls]

Auto-opened by session-dashboard for session keen-owl-601.
Pushing to session/keen-owl-601 advances this PR.

Worker attestation

Before flipping this PR to ready for review, confirm each item:

• Title describes the change (not the session id or branch).
• PR body summarises what and why (replace the TODO below).
• Tests run: name the command (e.g. npm test, cargo test) and the result.
• If this closes a work item, the body contains a Closes #N directive.
• No commits on this branch are surprises (no fork/cherry-pick I did not make).
• No secrets / credentials / large binaries staged.

Summary

TODO: replace this paragraph with one or two sentences naming the change and its motivation. Reviewers read this first.

Test plan

• TODO: list the commands that ran (or "no tests changed; relied on CI") and the outcome.

[briansrls]

Withdrawn: E0308 next-wave RCA is dashboard/PM planning content only per #4192/#4200 posture (manager vivid-lynx-81). No gunbc docs/planning landing; fanout work items spawned from receipt.