fix(webui): Construct browser tab title identifies the session

[edwin-zvs]

Summary

• Replace the stale pre-rename browser tab title agentd · remote with Construct.
• Keep document.title in sync with the session/service header chrome via setSessionChromeTitle, so multi-tab users can tell open sessions apart (<session title> · Construct, falling back to Construct when nothing is selected).

Closes #1077

Test plan

• Open the web UI and confirm the browser tab says Construct before selecting a session
• Select a session and confirm the tab becomes <session title> · Construct (matching the header)
• Rename the current session and confirm the tab title updates
• Open a service view and confirm the tab shows service · <name> · Construct
• Clear/deselect the current session and confirm the tab falls back to Construct
• Grep the rendered UI chrome for user-visible "agentd" (title only; localStorage keys / protocol schemes are out of scope)