Pre-Run cost estimate + cheap a11y-text-only Runs

[0Calories]

Type: AFK · Source: PRD v1 · Stories: 29, 30, 31

What to build

Pre-Run cost controls: a per-Run cost estimate derived from Perception Mode × step budget (aware of the selected model's pricing), shown before launch in the Dashboard and CLI; a model swap control via the Model Provider port (default Claude Sonnet 4.6); and a cheap a11y-text-only Run preset (e.g. Claude Haiku 4.5) so many sessions can be run inexpensively.

Acceptance criteria

• The cost estimate is computed from Perception Mode × step budget × selected model pricing and shown before a Run starts
• The model is selectable per Run, defaulting to Claude Sonnet 4.6
• The a11y-text-only cheap preset runs end-to-end at the lowest cost tier
• The estimate is sanity-checked against actual usage on a real Run (order-of-magnitude correctness)

Blocked by

• Bud Model + Calibration: traits resolve, budgets bind #4
• Perception Modes incl. a11y-only + perception_miss Finding #6