Remove the separate Agent workspace tab

[tonyfresher]

Remove the separate Agent workspace tab. Chats stay available in the docked sidebar and resizable popup on Overview, Scratchpad, and views, with shared ChatPanel props and simpler close-button handling.

The tab bar and CLI now expose only these destinations:

Overview     moi:/overview
Scratchpad   moi:/scratchpad
<view name>  moi:/views/<id>

Stacked on tinkering/view-chats; the diff contains only the Agent tab removal and related cleanup.

• Saved tab lists discard obsolete entries through the existing normalizer. Histories, settings, and pins remain intact; no workspace migration is added.
• Old Agent URLs show the existing unavailable page and Overview recovery action. Agent backends and model settings remain unchanged.
• Pending views retain their Open chat action; the click handler now avoids passing a mouse event as draft text.

Verified with 139 tests across the affected workspace/navigation, chat, layout, context, and OpenClaw suites; typecheck, formatting, and diff checks pass. Lint reports existing warnings. Browser checks covered unavailable-page recovery, chat selection and pins, sidebar/popup switching and resizing, narrow screens, tab reordering, and pending/compiled view chats.

[molefrog]

@claude what will happen to users who update moi, but keep the old skill?

[claude]

Claude finished @molefrog's task in 19s —— View job

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Old skill after updating moi

Short answer: nothing breaks. The only change to the skill in this PR is wording. The old copy would keep working.

What the skill change is

• The PR edits one sentence in workspace/.claude/skills/moi-workspace/SKILL.md. It used to say chats are reachable "or on a dedicated page". Now it says "through the docked sidebar or floating popup".
• I grepped the skill for moi:/agent, "Agent tab" and 'agent'. It has no instructions that depend on the Agent tab. An old copy doesn't tell the agent to open anything that no longer exists.

What an old-skill user would see

• The agent's skill still says chats live "on a dedicated page". That is slightly wrong, but it only affects how the agent describes the app to the user.
• If the agent tries moi:/agent, parseMoiHref in lib/navigation.ts already rejected it before this PR, with Unsupported workspace destination. Now tabFromPath also fails for it, so the error is the same. The CLI's moi tabs output no longer lists Agent. assertNavigableTab lists the valid addresses in its error, so the agent can recover.
• A browser already open on moi:/agent shows the existing unavailable page with the Overview recovery action. Saved tab lists drop the entry through normalizeTabsState.

The skill version isn't bumped

• SKILL.md still ends with <moi-skill version="0.20.0" />, and this PR doesn't change it. server/skill-version.ts only treats a gap of at least a minor version as worth prompting for. Patch gaps stay silent.
• If this PR doesn't bump the marker, users with the old copy will never be prompted to update. Their copy stays on the old wording until a later release bumps the version.
• That seems fine for a one-sentence fix. If you want the new wording to reach existing workspaces, bump the marker to 0.21.0. That makes isMinorBehind true, and the agent and the frontend update check will flag it.

I didn't change any files.

[molefrog]

LGTM!