feat(tui): show pricing & capabilities in /model picker

[dgageot]

The /model dialog now reads as a proper table with a details panel,
making it much easier to compare models and pick one. Catalog metadata
(pricing, context window, modalities, family) is pulled best-effort
from the models.dev store and surfaced both inline and in a stable
panel below the list.

What changes

Runtime

• runtime.ModelChoice gains optional fields populated from models.dev
  (Family, InputCost, OutputCost, CacheReadCost,
  CacheWriteCost, ContextLimit, OutputLimit, InputModalities,
  OutputModalities).
• LocalRuntime populates them for both configured models and catalog
  entries via small populateCatalogMetadata / applyCatalogMetadata
  helpers. Slice fields are cloned with slices.Clone so the
  models.dev cache stays immutable through ModelChoice.

TUI

• The model list is now a 3-column table: name + badges on the left,
  then right-aligned Input/1M, Output/1M, and Context
  columns, with a static column header above. Missing values render
  as muted em-dashes.
• The inline provider/model description has moved out of the row
  into a 4-line details panel below the list:
  • Reference — provider/model (and family if not redundant)
  • Pricing — input, output, cache read/write, per 1M tokens
  • Limits — context window + max output
  • Modalities — text, image → text
• The panel keeps a stable height; missing data is rendered as
  "unavailable" so the dialog never resizes.
• Styling lives in pickerRowPalette / detailsStyles instead of
  being threaded through renderer arguments. renderModel is now a
  three-line composition over renderRowName + renderRowStats, and
  the row + header share pickerNameColWidth for the table layout.
• formatCostPerMillion keeps four decimals for sub-cent prices so
  values in (0, 0.005) don't collapse to a misleading "$0.00".

Tests

• New tests cover the formatting helpers
  (formatCostPerMillion, formatContextCell, rightAlign,
  modelReference) and dialog rendering: column headers and per-row
  stats are present, the provider/model reference is gone from rows,
  the details panel exposes the full breakdown, and missing-info
  models fall back to "unavailable".

Preview

╭──────────────────────────────────────────────────────────────────────────────────────────────╮
│                                         Select Model                                         │
│                                                                                              │
│  > Type to search or enter custom model (provider/model)…                                    │
│  ──────────────────────────────────────────────────────────────────────────────────────────  │
│                                                                Input/1M Output/1M Context    │
│  default_model (current)                                           $2.5       $10  128.0K    │
│  ── Other models ──────────────────────────────────────────────────────────────────          │
│  Claude Sonnet 4.5                                                   $3       $15  200.0K    │
│  Gemini 2.5 Flash                                                 $0.30      $2.5    1.0M    │
│  ──────────────────────────────────────────────────────────────────────────────────────────  │
│  Reference   anthropic/claude-sonnet-4-5 · claude family                                     │
│  Pricing     $3 in · $15 out · $0.30 cache read · $3.75 cache write · per 1M tokens          │
│  Limits      200.0K context window · 8.2K max output                                         │
│  Modalities  text, image → text                                                              │
│                                                                                              │
│                            ↑/↓ navigate  enter select  esc cancel                            │
╰──────────────────────────────────────────────────────────────────────────────────────────────╯

Validation

mise lint, full mise test, and mise build all pass.

Assisted-By: docker-agent