fix(desktop): open chats from the skills view

[WillieTheWhale]

What changed

Clicking a sidebar session now returns to its chat when Skills & Tools is open. Sessions displayed in a separate tile still focus that tile instead.

Why

The click handler treated the main chat and separate tiles as the same surface, so it swallowed the navigation back to chat.

Tests

• Desktop test suite: 2,208 passed, 2 skipped
• Typecheck and lint passed

Fixes #68302

[alt-glitch]

This was generated by AI during triage.

Duplicate of #66880: both repair the Desktop full-page session-click routing defect. #66880 already covers /skills and the open-tile case; this patch should not replace that broader regression coverage.

[teknium1]

Thanks for the focused Desktop regression fix. This is now redundant on current main.

• Automated hermes-sweeper review verified that ecf8ef970ee137e55c1fcf4028ca9affef767db9, merged through fix(desktop): clicking the active session from a full page returns to the chat #71901, already fixes the active-main-session click behind full-page views such as Skills.
• apps/desktop/src/app/open-session.ts:83-89 routes back to the selected chat when focusedSessionNeedsRoute(...) identifies a main session covered by a workspace page.
• apps/desktop/src/store/session-states.ts:630-636 deliberately keeps an open tile visible while routing a covered main session, and apps/desktop/src/store/session-states.test.ts:48-65 covers those cases.
• This matches the prior duplicate report on fix(desktop): switch to chat when resuming the open session from a full-page tab (#66875) #66880, whose discussion records that the upstream fix superseded the same behavior.

Closing as implemented on main.