Center the composer on a fresh chat

[gary149]

Before the first message the composer no longer sits at the bottom of an
empty column: it centers vertically with the app greeting above it, and
docks to the bottom as soon as the conversation has content — the layout
every other chat app uses for its new-chat screen.

• ChatWindow: the composer overlay switches between bottom-0 (docked)
  and bottom-1/2 translate-y-1/2 (centered). Pure CSS, so server-rendered
  markup already lands centered and nothing jumps on hydration.
• max-h-full + justify-end clamp the centered box to the column height,
  so a group taller than the viewport (long draft plus attachments on a
  short screen) falls back to the docked position instead of pushing the
  send button below the fold.
• The greeting moved out of the scroll column and above the composer;
  clientHeight is now bound to an inner wrapper so the greeting can never
  inflate the clearance the scroll spacer derives from it.
• Touch devices dock while the input is focused: the virtual keyboard
  covers the lower half of the screen and fires no ResizeObserver, so a
  centered composer would end up behind it.
• "Fresh" counts rendered messages only, so a conversation created but
  never sent to — it still carries an invisible system preprompt message
  — gets the same screen instead of a blank column, and the example chips
  and caveat line show there too.

Verified in Chromium (desktop 1280x800/520, tablet, iPhone 13 portrait and
landscape, 320x568) against both dev and production builds: centering is
exact in every viewport, docking is unchanged after a send, and the
keyboard-focus/blur, attachment, drag-drop and dropdown paths all behave.
469 unit tests and 32 e2e specs pass.

Co-Authored-By: Claude Opus 5 noreply@anthropic.com
Claude-Session: https://claude.ai/code/session_011s35VQavGEgfwSAR15kuok

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve row geometry for disabled MCP preferences

When a returning user has disabled one of the configured base MCP servers, the SSR branch still treats baseMcpServerCount > 0 as though all servers were enabled and reserves the hidden examples row. During hydration, initWithServers restores the disabled IDs from localStorage, $allBaseServersEnabled becomes false, and this expression removes the row for a fresh non-router tool model, visibly shifting the newly centered composer. Avoid changing the reservation solely when the client-side disabled-server preference hydrates.

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[gary149]

Confirmed and fixed in 9793147. Reproduced at 1280x800 by writing a configured base server's id into chatui:mcp:disabled-base-ids: input top 406 at SSR paint, 388 after hydration.

Worth noting it's wider than "disabled servers" — allBaseServersEnabled requires every base server to be selected, so turning off a single one is enough to trigger it.

The reservation now reads only the configured base-server list from the SSR payload, which server and client agree on, and $allBaseServersEnabled moves to the chips-visibility condition where the client is the authority. The trade is that a user in this state keeps an empty reserved row on a non-router tools model — invisible whitespace in a centered layout, where a jump on every page load is not.

Verified across SSR paint, hydration and first keystroke in three configurations: base servers enabled (chips show, 406/262 throughout), every base server disabled (row reserved and empty, 406/262 throughout), and MCP_SERVERS=[] (nothing reserved, 388/280 throughout).

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