fix(pi): focus composer when clicking chat thread

[jonathanlab]

Problem

Clicking a Pi chat thread did not focus its composer, unlike ACP threads.

Changes

• Focus the Pi composer after clicks on non-interactive thread content.
• Share the ACP click guard so interactive elements and text selection retain their expected behavior.

How did you test this?

• pnpm exec biome check packages/ui/src/features/pi-sessions/PiSessionView.tsx packages/ui/src/features/sessions/components/SessionView.tsx packages/ui/src/features/sessions/components/focusComposerOnPaneClick.ts packages/ui/src/features/sessions/components/focusComposerOnPaneClick.test.ts
• pnpm --filter @posthog/ui exec vitest run src/features/sessions/components/focusComposerOnPaneClick.test.ts
• pnpm --filter @posthog/ui typecheck

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

[trunk-io]

😎 Merged directly without going through the merge queue, as the queue was empty and the PR was up to date with the target branch - details.

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 42c63f4.}

[greptile-apps]

_{Reviews (1): Last reviewed commit: "fix(pi): focus composer when clicking ch..." | Re-trigger Greptile}

[github-actions]

Small, contained frontend fix that extracts and reuses an existing click-guard helper for composer focus, matches its description exactly, includes new tests, and touches no risky territory.

• Author wrote 100% of the modified lines and has 10 merged PRs in these paths (familiarity STRONG).
• 👍 on the PR from greptile-apps[bot].

Gate mechanics and policy version

Gate		Result
prerequisites	✓	all clear
deny-list	✓	no deny categories matched
size	✓	49L, 3F substantive, 102L/4F incl. docs/generated/snapshots — within ceiling
tier	✓	T1-agent / T1c-medium (102L, 4F, single-area, fix)
stamphog 2.0.0b3		.stamphog/policy.yml @ 0ed50b9 · reviewed head 42c63f4