Agent composer helper and run-mode text miss WCAG contrast

Agent composer text misses 4.5:1 contrast.

- Four rendered text instances fail axe.
- Measured ratio: 4.33:1.
- Reproduced on deployed frontend `67de497a8112c109688e8cb1bbf648759aa6e46f`.

Full context for agent readers

## Problem

The V1 agent composer uses `#8a8a8a` text on `#262729` at 12–14 px. axe-core 4.10.3 measures 4.33:1, below the WCAG AA 4.5:1 threshold for normal text.

Affected rendered text:

- `Describe ideas, @ to reference,`
- `add nodes from graph,`
- `or drag in assets`
- run-mode label `Ask`

## Reproduction

1. Authenticate at `https://agent.comfy.org/`.
2. Enable the `agent-in-app-experience` flag in the browser context and open the agent panel.
3. Run axe with `wcag2a,wcag2aa,wcag21a,wcag21aa,wcag22aa` against `#agent-panel-root`.
4. Observe one serious `color-contrast` rule with four failing nodes.

## Expected

All normal-size composer helper and mode text reaches at least 4.5:1 in the rendered theme without weakening other component states.

## Acceptance criteria

- The four named text instances meet at least 4.5:1 in the deployed dark theme.
- axe reports no `color-contrast` violation for the agent panel in this state.
- A component or browser accessibility test protects the token/treatment.

## Evidence

- axe-core: 4.10.3
- Scan time: 2026-09-02T05:41:57Z
- Surface: `https://agent.comfy.org/`
- Served commit: `67de497a8112c109688e8cb1bbf648759aa6e46f`
- Program artifact: `reports/qa/2026-09-02-a11y-evidence/axe-results.json`