fix(coding-agent): respect role thinking for temporary model picks

[roboomp]

Repro

A focused session repro configured modelRoles.smol = google-antigravity/gemini-3.5-flash:high, verified the role resolver returned high, then called setModelTemporary(selectedModel) as the temporary picker did. Before the fix, bun test tmp-repro-5290.test.ts failed with Expected: "high"; Received: undefined for session.thinkingLevel.

Cause

packages/coding-agent/src/modes/controllers/selector-controller.ts handled the Model Hub onPick callback by calling session.setModelTemporary(model) without resolving explicit thinking metadata from configured roles. AgentSession.setModelTemporary() only applies a thinking level when its caller passes one, so the temporary picker bypassed the same role-thinking resolution used by role cycling in AgentSession.getRoleModelCycle() / applyRoleModel().

Fix

• Added AgentSession.resolveTemporaryModelThinkingLevel() to scan configured model roles, resolve their model selectors with existing match preferences, and return the explicit thinking suffix when a temporary pick matches that role's resolved model.
• Updated the temporary Model Hub picker (Alt+P, /switch, /model --temporary) to pass that resolved thinking level into setModelTemporary() while keeping the switch session-only.
• Added regression coverage for google-antigravity/gemini-3.5-flash:high so temporary picks apply the role override instead of falling back to the model/default thinking state.
• Updated the coding-agent changelog under [Unreleased].

Verification

bun test packages/coding-agent/test/agent-session-role-thinking.test.ts -t temporary passed with 1 test, 5 assertions. bun test packages/coding-agent/test/agent-session-role-thinking.test.ts passed with 20 tests, 112 assertions. bun run check in packages/coding-agent passed. Fixes #5290