UX: Auto-resize the AI bot docked composer with content

[SamSaffron]

Adds an @autoResize mode to the shared DockedComposer so the input
grows with its content up to a viewport-bounded max height instead of
requiring a manual resize handle. The textarea path uses CSS
field-sizing: content (with a JS fallback for older browsers), while
the rich editor relies on a capped max-height with internal scroll.

The AI bot docked composer adopts the new mode and drops its custom
resize-handle styling. The --docked-composer-max-resize-offset custom
property is now kept in sync on viewport and window resize so the cap
tracks available space on mobile keyboards.

Internally renames textarea to inputElement since the reference can
now point at either a <textarea> or the ProseMirror contenteditable.

[keegangeorge]

Looks great! Thank you!

[SamSaffron]

@patch-triage can you rebase?

[SamSaffron]

@patch-triage ... fix linting

[discourse-patch-triage]

Applied suggestions and committed the fix.

Fix indentation linting in docked composer components

• frontend/discourse/app/components/docked-composer.gjs
• plugins/discourse-ai/assets/javascripts/discourse/components/ai-bot-docked-composer.gjs

69720b4

[SamSaffron]

@patch-triage oh my ... previous commit utf-8 mangled some lines fix that

[discourse-patch-triage]

Could not apply all suggestions:

• frontend/discourse/app/components/docked-composer.gjs: search string not found — the code may have already changed or the suggestion is stale. Copy the exact text from read_file output:

// Reusable chat-style "docked" composer. There is deliberately no
// markdown-preview toggle  users who want to see rendered output
// switch to the rich editor via the toolbar's RTE toggle, which is

• frontend/discourse/app/components/docked-composer.gjs: search string not found — the code may have already changed or the suggestion is stale. Copy the exact text from read_file output:

// @onSubmit is required; all other args are optional. See the
// styleguide entry (/styleguide  Organisms  Docked Composer) for
// the live API surface.

• frontend/discourse/app/components/docked-composer.gjs: search string not found — the code may have already changed or the suggestion is stale. Copy the exact text from read_file output:

      // Falsy return  don't clear; consumer can short-circuit on
      // validation failure without losing the user's input.
      if (!result) {