feat(tui): show optional daily session cost

[zbcoding]

Issue for this PR

Related to #39740. Session cost is already visible in the sidebar Context section, but users also need an optional total for all sessions updated today without running opencode stats --days 1.

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Adds an optional Today cost below the existing session spend in the sidebar Context section. The footer is unchanged. The display is:

$0.21 spent
$0.56 today

When the current session's model has no pricing information (e.g. a custom model without a cost entry in the catalog or config), the spent line reads N/A spent instead of $0.00 spent, since the true cost cannot be derived. The footer session-cost display is unchanged.

Today is calculated from every session in the shared local database updated since local midnight. It is therefore shared across concurrently running OpenCode terminals and each Context view refreshes it every 30 seconds. The current session spend is fetched from the persisted session record as well. If a value cannot be fetched, it is omitted.

The Today line is disabled by default and appears only when show_today_cost is set to true. Create ~/.config/opencode/tui.json if it does not exist:

{
  "$schema": "https://opencode.ai/tui.json",
  "show_today_cost": true
}

A project-local .opencode/tui.json can also be used. The daily aggregation is exposed through the typed session API and does not shell out to opencode stats --days 1.

Why the diff touches so many files

The hand-written change is small: the endpoint (packages/protocol/src/groups/session.ts, packages/server/src/handlers/session.ts, packages/core/src/session.ts), the TUI config flag, and the sidebar Context view (including the N/A spent fallback). Everything else is regenerated output:

• packages/client/src/generated-effect/client.ts and packages/client/src/generated/*.ts — generated by @opencode-ai/httpapi-codegen (// Do not edit header), adding the typed session.cost client method. The endpoint is registered last in the session group so the generator's positional Endpoint3_N constants keep their existing names and the generated diff is append-only. Route matching is unaffected: the router (find-my-way-ts) prioritizes the static /api/session/cost segment over /api/session/:sessionID regardless of registration order.
• packages/sdk/js/src/v2/gen/*.ts — the hey-api codegen adding the same cost() method to the SDK.
• packages/plugin/src/tui.ts — the TuiConfigView type gains the resolved show_today_cost field so plugins see the setting.
• packages/opencode/src/cli/cmd/stats.ts — refactored to reuse the new sumSessionCosts helper instead of accumulating cost inline (same output, one code path for cost summation).

Note on attribution: the total sums the full cost of every session with time_updated since local midnight. A long-running session that started yesterday and is touched today counts its entire cost toward today. This is a deliberate simplification for a glanceable stat; exact per-day attribution would require message-level aggregation.

How did you verify your code works?

• bun typecheck passed in packages/plugin, packages/sdk/js, and packages/tui.
• The focused session-cost test passed.
• Built and smoke-tested the local Linux binary with --version.
• Rebased onto the latest origin/dev before updating this PR.
• Confirmed the sidebar shows N/A spent when the session model has no pricing and the currency amount when it does.

The repository-wide pre-push typecheck is currently blocked by unrelated AWS stats client type errors and a Bun/tsgo segmentation fault.

Screenshots / recordings

This is a terminal UI change. Expected sidebar Context output with the setting enabled:

Context
12,345 tokens
42% used
$0.21 spent
$0.56 today

For a model without pricing information:

Context
12,345 tokens
42% used
N/A spent

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search, I found related PRs that touch on cost display and TUI footer enhancements, but no direct duplicates of PR #39807:

Related PRs (not duplicates, but in similar areas):

• PR feat(tui): hot-reload local TUI plugins #39776 - feat(tui): hot-reload local TUI plugins - Different feature, but same TUI area
• PR feat(tui): show estimated live token throughput in footer #30164 - feat(tui): show estimated live token throughput in footer - Related footer enhancement, but for different metric
• PR feat(tui): show subagent cost rollup in sidebar and task history #25712 - feat(tui): show subagent cost rollup in sidebar and task history - Related cost display, but for subagent costs in different location
• PR feat(opencode): add codex estimated cost flag #35131 - feat(opencode): add codex estimated cost flag - Related cost tracking feature

None of these address the specific feature of showing optional daily session cost in the TUI footer with the 30-second refresh and midnight-based calculation that PR #39807 implements.

No duplicate PRs found

[github-actions]

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[github-actions]

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