feat(desktop): Runtime identity/context panel (ADR #19)

[brettchien]

Drafted by Orca (ecs-claude) — flagging authorship (shared GitHub identity).

The desktop panel the ADR #19 read model was built for — surfaces "who am I managing this cluster as, against what account?" in the Studio skin. Follows the merged CP/MCP slices (#20/#21/#23).

What:

• src-tauri — a runtime_context bridge command (mirrors deploy_list) that calls the bundled oab-mcp sidecar's runtime_context tool.
• console — RuntimeContext view-model + a Source method (Tauri bridge + Mock fixture); a pure identityHtml renderer showing principal / account / region / source / binding, a role-vs-static-user kind badge, and an IdentityMismatch highlight (red left-border + ⚠ … expected <arn>) when the resolved principal fails the binding's expected_principal. Fetched once on boot (identity changes rarely; each call is a live STS lookup server-side); the browser build renders from a fixture.

Effect: today's deploy_list incident would render as a red panel — user/brett.chien (kind user) in 916371022086, identity mismatch — expected …:role/openab-orca-task-role.

Verification (local, since desktop CI runs tsc && vite build but not vitest):

• tsc --noEmit clean · vitest 14/14 (6 new identity tests) · vite build OK.
• The Rust bridge is a small mirror of deploy_list; desktop.yml compile-linux compiles it.

Screenshots to follow once a desktop build is bundled. Relates to #19.

🤖 Generated with Claude Code

[brettchien]

Merged to main as 82a9689 (squash, all 9 files). GitHub's API was returning 502s during the merge — the squash commit landed on main but the PR's merged flag didn't flip, and the head-branch deletion then marked this PR closed rather than merged. The change is fully on main; this is a metadata artifact of the outage, not an abandoned PR.