Render session widgets in web UI

[edwin-zvs]

Summary

• Render file-backed session widgets in the web UI from SessionDetail.ui_panels
• Add a widgets dropdown with persisted per-session visibility in localStorage
• Support basic widget Markdown, nested checklists, :::timeline / :::agentd-timeline, and inline agentd:action/... links
• Dispatch widget actions through session.input as OBSERVATION: ui.action ...
• Support explicit ?key= shortcut display/dispatch only while a widget card has focus

Manual QA

Using an isolated daemon (AGENTD_WEBUI_PORT=5876) with a timeline-demo.md widget:

• Verified widget appears in the web UI for the selected session
• Verified timeline renders with nested checklist items and keyed actions ([d] Start demo, [r] Run checks)
• Verified dropdown toggles visibility and persists hidden state in localStorage
• Verified re-showing through dropdown restores the widget
• Verified clicking Run checks sends OBSERVATION: ui.action ... into the session transcript

Validation

• node --check on extracted index.html script
• cargo build -p agentd
• cargo build -p agentd-cli (for isolated smoke-test CLI)
• git diff --check

[edwin-zvs]

Updated per feedback:\n\n- Moved the web widget trigger to a top-right overlay control (), positioned left of the terminal controls when those are visible.\n- Changed widget content to a top-right popover instead of a full-width section.\n- Raised web browser preview z-order above widget popovers.\n- Adjusted TUI render order so browser preview redraws after dynamic UI widgets/popovers and stays on top.\n\nValidation rerun:\n- on extracted web script\n- \n- \n- Browser smoke test verified the button has a visible top-right rect and opens a 420px popover.

[edwin-zvs]

Updated per feedback:

• Moved the web widget trigger to a top-right overlay control labeled widgets, positioned left of the terminal top/bottom controls when those are visible.
• Changed widget content to a top-right popover instead of a full-width section.
• Raised web browser preview z-order above widget popovers.
• Adjusted TUI render order so browser preview redraws after dynamic UI widgets/popovers and stays on top.

Validation rerun:

• node --check on extracted web script
• cargo build -p agentd -p agentd-cli
• git diff --check
• Browser smoke test verified the widgets button has a visible top-right rect and opens a 420px popover.

[edwin-zvs]

Follow-up polish from web hot-reload review:

• Suppressed the first markdown heading inside widget card bodies when it is already used as the card title, avoiding duplicate titles.
• Capped the web widget popover to max-width/max-height 80% of the session view.
• Strengthened timeline connector styling so the vertical bar is visible between timeline rows.

Validation:

• node --check on extracted web script
• cargo build -p agentd -p agentd-cli
• git diff --check
• Browser smoke test confirmed body no longer repeats the title, connector style is present, and popover size is below 80% of the view.

[edwin-zvs]

Follow-up from web UI review:

• Put the terminal-mode widgets control into the same top-right control row as top/bottom, ordered widgets → top → bottom, so top/bottom remain visible when widgets exist.
• Kept the chat/headless fallback widgets control for views that do not show terminal top/bottom controls.
• Re-aligned the widget popover to the right edge of the session view instead of the widgets button edge.
• Reworked timeline connectors onto a dedicated rail column so the vertical line spans rows with nested checklist items.

Validation:

• node --check on extracted web script
• cargo build -p agentd -p agentd-cli
• git diff --check
• Browser smoke test confirmed popover right edge alignment and timeline rail CSS; terminal-mode row is covered by DOM/control-row ordering.

[edwin-zvs]

Final widget visual polish:

• Removed the inner widget-card border/background so the popover presents as a single bordered surface.
• Kept the title/body divider and added a simple separator only between multiple widget cards.

Validation:

• node --check on extracted web script
• cargo build -p agentd
• git diff --check