feat(tui): lay the token meter legend out in aligned columns

[edwin-zvs]

Two legend readability fixes, both about a row that names a band in the graph above it.

Aligned columns

The legend flowed entries end-to-end, so every row started its names at a different offset. Past a handful of models the dots and names scattered into a block of text with no line to read down.

It now lays out as a grid of equal-width cells, sized to the widest entry, so column n starts at the same x on every row:

--- before (flow) ---
|● claude-opus-5 4.8k/s ● claude-sonnet-5 1.2k/s |
|● gpt-5.5-codex idle ● grok-4 310/s ● gemini-3-pro 90/s |
|● claude-haiku-4-5 idle ● qwen3-coder 2.4k/s |

--- after (grid, col_w=25) ---
|● claude-opus-5 4.8k/s   ● claude-sonnet-5 1.2k/s |
|● gpt-5.5-codex idle     ● grok-4 310/s           |
|● gemini-3-pro 90/s      ● claude-haiku-4-5 idle  |
|● qwen3-coder 2.4k/s     |

(That block is the layout code's own output for a 64-column panel, printed from a throwaway test — not a screenshot. Seven models at once is hard to stage in a demo daemon; the alignment is what the diff is about.)

Tradeoffs taken deliberately:

• Cells are sized to the widest entry, packing left. Spreading them to fill the width would squeeze the right-aligned Σ fleet total off a full row; the slack at the right edge is where it lives.
• A cell never spills into its neighbour — one long name shifting the column below it undoes the alignment the grid exists for. It truncates within its cell instead, dropping the rate before the name as before.
• It can cost a row. Flow fit the seven above in three rows, the grid takes four. The legend's row budget (everything above the graph's 3-row floor) is unchanged, and anything past it is still counted as +N.
• An entry wider than the whole panel still gets one column and is truncated — zero columns would name nothing.

idle keeps the model's color

Follow-up to #1061, which dimmed idle by blending 70% toward the neutral gray. Half-graying the word made a quiet model's row stop pointing at its band. It now uses the model name's exact color with Modifier::DIM, so only the weight changes. IDLE_RATE_DIM and the blend_color call are gone.

Testing

cargo test --workspace green (0 failures). New/updated unit tests cover column alignment, the row budget, the one-column floor, and the idle style keeping its fg while gaining DIM.

Spec 0167 updated for both decisions.

Binaries

Only crates/cli changed → the relevant binary is construct:

/Users/moon/agentd/.claude/worktrees/idle-rate-same-color/target/debug/construct