Merge upstream waypoint C (kenn-io kenn-io#991 export v1 + kit-ui/service layer)

Waypoint C of the staged upstream catch-up (specs/merge-upstream-waypoints.md).
Merges u/main up to 725a3d0 (126 commits: export v1 foundation, the
export.PricingResolver cost model, a service layer for usage summaries, the
kit-ui component library + TopBar/theme, i18n, pairwise usage comparison, new
Activity/RecentEdits nav) into our branch.

Pricing (thread the fork's 1h cache-write rate through export.PricingResolver
without touching the frozen export v1 wire contract):
- Add an internal, non-serialized CacheWrite1hPerMTok to export.ModelRates
  (no canonical_json key, no EffectiveModelRate field -> digest/wire stay
  byte-identical), populated from db.ModelPricing.CacheCreation1hPerMTok in
  loadPricingMap/modelPricingRates with the defensive 5m fallback.
- Restore the 5m/1h split in dailyUsageAmounts and sessionRowCost via a new
  parseEphemeralCacheSplit helper (upstream's rewritten token parser skips the
  nested cache_creation object), computing cost inline so 1h bills at its rate.
- Drop the now-orphaned db.modelRates struct; the export resolver is the single
  cost source.

Usage summary: re-home the snapshot exporter's BuildUsageSummary onto the new
service layer (service.BuildUsageSummaryResult + usageSummaryResponseFromService),
since the fold*/computeCacheStats helpers moved into internal/service.

Frontend: adopt kit-ui's TopBar header, filtering the nav `tabs` to hide
curation routes in snapshot mode (replaces the old {#if !SNAPSHOT} nav);
adopt kit-ui theme getters/setters in ui.svelte.ts; keep the fork's 24-color
golden-angle + org-theming projectColor over kit-ui's hashColor; coexist the
longestPrompts panel with the new pairwise-comparison panel in the usage store
(Endpoint now spans summary|comparison|pairwise|topSessions|longestPrompts).

CLI: `usage projects` and `usage longest-prompts` adopt the paired
--format/--json convention upstream now enforces.

Deferred (unchanged from B): 1h-cache parity for the PostgreSQL and DuckDB cost
paths; SetSessionPrivate stays read-only on the PG store.

Green: go build/vet/test (except the snapshot test needing a git `origin`
remote), svelte-check, 1770 vitest tests, make build.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: ryan-williams

.agents/skills/localization-paraglide/SKILL.md

@@ -0,0 +1,48 @@
+---
+name: localization-paraglide
+description: Use when adding, reviewing, or fixing localized UI copy in agentsview's Svelte frontend with Paraglide JS. Trigger for frontend/messages/*.json edits, generated m.* message usage, locale-aware number/date/relative-time formatting, pluralization, language switching, or hard-coded user-facing English in frontend/src.
+---
+
+# Localization Paraglide
+
+## Workflow
+
+1. Read `frontend/project.inlang/settings.json`, `frontend/src/lib/i18n/index.ts`,
+   and nearby localized components before editing.
+2. Put user-facing copy in `frontend/messages/en.json` and
+   `frontend/messages/zh-CN.json` with identical keys.
+3. Import app localization through `frontend/src/lib/i18n/index.ts`:
+
+   ```ts
+   import { m } from "../../i18n/index.js";
+   ```
+
+4. Call generated Paraglide messages as functions, for example
+   `m.nav_sessions()` or `m.shared_active_filters_remove_agent({ agent })`.
+5. Use Paraglide message declarations for plural, number, datetime, and relative
+   time when the formatted value is part of translatable copy.
+6. Use `formatDateTime()` from `frontend/src/lib/i18n/index.ts` for standalone
+   visible date/time labels that need the active Paraglide locale.
+7. Keep technical identifiers untranslated: agent names, model names, file paths,
+   CLI commands, IDs, and raw API values.
+8. Run `npm run i18n:compile` and `npm run check` from `frontend/` after message
+   or component changes.
+
+## Message Rules
+
+- Keep key names scoped and descriptive, such as
+  `settings_terminal_title` or `activity_concurrency_empty`.
+- Do not concatenate translated sentence fragments. Prefer one complete message
+  with parameters.
+- Pass numbers as numbers to pluralized messages. Pass strings only for display
+  fragments that have already been intentionally formatted.
+- In Svelte, put arrays or objects containing translated labels in `$derived` or
+  `$derived.by` when they must update after locale changes.
+- Do not import from `frontend/src/lib/paraglide/*` directly in components unless
+  changing the i18n wrapper itself.
+
+## Formatting
+
+Read `references/paraglide-formatting.md` when adding pluralization, ordinal
+rules, date/time formatting, relative dates, compact numbers, currencies, or
+mixed selector messages.

.agents/skills/localization-paraglide/agents/openai.yaml

@@ -0,0 +1,4 @@
+interface:
+  display_name: "Paraglide Localization"
+  short_description: "Use Paraglide localization correctly"
+  default_prompt: "Use $localization-paraglide to localize this agentsview UI change with Paraglide."

.agents/skills/localization-paraglide/references/paraglide-formatting.md

@@ -0,0 +1,180 @@
+# Paraglide Formatting Reference
+
+Official docs:
+
+- Basic usage and generated messages:
+  <https://github.com/opral/paraglide-js/blob/main/docs/basics.md>
+- Variants and plural selectors:
+  <https://github.com/opral/paraglide-js/blob/main/docs/variants.md>
+- Number, datetime, and relative-time formatting:
+  <https://github.com/opral/paraglide-js/blob/main/docs/formatting.md>
+
+## Generated Messages
+
+Use generated message functions through the app wrapper:
+
+```ts
+import { m } from "../../i18n/index.js";
+
+m.greeting({ name: "Ada" });
+```
+
+Messages live in `frontend/messages/{locale}.json`. The English and Simplified
+Chinese catalogs must have the same keys.
+
+## Cardinal Plurals
+
+Use variant messages for counts. Paraglide's `plural` selector uses
+`Intl.PluralRules`, so it works for locales with more than English singular and
+plural categories.
+
+```json
+{
+  "tool_call_group_call_count": [
+    {
+      "declarations": [
+        "input count",
+        "local countPlural = count: plural"
+      ],
+      "selectors": ["countPlural"],
+      "match": {
+        "countPlural=one": "{count} tool call",
+        "countPlural=other": "{count} tool calls"
+      }
+    }
+  ]
+}
+```
+
+Call with a number:
+
+```ts
+m.tool_call_group_call_count({ count: 3 });
+```
+
+For `zh-CN`, use the same declaration and provide the matching locale text; a
+single `other` or wildcard branch is often enough only when the locale truly has
+no visible plural distinction.
+
+## Ordinals
+
+Use `type=ordinal` for values such as 1st, 2nd, and 3rd.
+
+```json
+{
+  "ranking_place": [
+    {
+      "declarations": [
+        "input place",
+        "local placePlural = place: plural type=ordinal"
+      ],
+      "selectors": ["placePlural"],
+      "match": {
+        "placePlural=one": "{place}st",
+        "placePlural=two": "{place}nd",
+        "placePlural=few": "{place}rd",
+        "placePlural=*": "{place}th"
+      }
+    }
+  ]
+}
+```
+
+## Date And Time
+
+For dates inside translatable copy, use the Paraglide `datetime` formatter in the
+message declaration so locale formatting and word order stay in the catalog.
+
+```json
+{
+  "session_started_at": [
+    {
+      "declarations": [
+        "input startedAt",
+        "local started = startedAt: datetime dateStyle=medium timeStyle=short"
+      ],
+      "match": {
+        "startedAt=*": "Started {started}"
+      }
+    }
+  ]
+}
+```
+
+For standalone visible date/time labels in components, use the app helper:
+
+```ts
+import { formatDateTime } from "../../i18n/index.js";
+
+formatDateTime(timestamp, {
+  month: "short",
+  day: "numeric",
+  timeZone,
+});
+```
+
+Do not hard-code `"en"` or `"en-US"` for visible UI formatting. It is acceptable
+to use a fixed locale for internal sentinel calculations when the formatted
+string is not displayed.
+
+## Relative Dates
+
+Use Paraglide's `relativetime` formatter. The `unit` option is required.
+
+```json
+{
+  "status_bar_synced_ago": [
+    {
+      "declarations": [
+        "input duration",
+        "local formattedDuration = duration: relativetime unit=minute numeric=auto"
+      ],
+      "match": {
+        "duration=*": "synced {formattedDuration}"
+      }
+    }
+  ]
+}
+```
+
+Use a variable unit only when the caller computes the unit intentionally:
+
+```json
+{
+  "updated_relative": [
+    {
+      "declarations": [
+        "input duration",
+        "input unit",
+        "local formattedDuration = duration: relativetime unit=$unit style=short"
+      ],
+      "match": {
+        "duration=*,unit=*": "Updated {formattedDuration}"
+      }
+    }
+  ]
+}
+```
+
+## Numbers And Currency
+
+Prefer Paraglide's `number` formatter for numbers embedded in messages:
+
+```json
+{
+  "usage_total_cost": [
+    {
+      "declarations": [
+        "input amount",
+        "local cost = amount: number style=currency currency=USD"
+      ],
+      "match": {
+        "amount=*": "Total cost {cost}"
+      }
+    }
+  ]
+}
+```
+
+Use raw `toLocaleString()` only for non-sentence labels where the browser or
+app-level locale behavior is already intentional.