Adoption polish: report effective review authority and superseded Devin bridge drift

[jeffhuber]

Problem

Three smaller adoption inconsistencies make the first-run report noisier than the configured posture:

• Session and audit output can call Claude/Codex a "merge-authority lane" even when the active repository profile keeps the lane informational.
• Setup drift recognizes legacy Devin bridge workflow names but does not clearly report that the issue-comment bridge is superseded by the maintained Sessions API v3 transport.
• A normal hosted-agent doctor run can emit many optional-provider warnings without a concise view scoped to the intended posture.

Outcome

Rendered status describes the repository's effective authority and transport, and setup drift gives a precise migration action for superseded Devin bridge files.

Acceptance criteria

• Render "merge-authority" only from the effective lane configuration used for this run; otherwise render "informational" or equivalent.
• Keep immutable historical fixtures recognizable without using their old wording as the current configured posture.
• Detect the legacy Devin issue-comment bridge/labeler workflow pair during setup drift and report a bounded superseded-transport migration action without deleting files automatically.
• Provide a concise posture-scoped doctor view or summary that retains full detail in JSON and explicit advanced/campaign modes.
• Preserve the Claude + Codex default and keep optional provider setup out of the initial path.
• Add wording, drift, no-Devin, privacy, and backwards-compatibility tests.
• Deliver after Devin v1.4.0; this P3 polish does not block Release: publish and qualify Code Mower v1.4.0 with Devin peer support #912.

Evidence

Reported from a metadata-only v1.3.1 hosted adoption rehearsal; no P0/P1 impact.