Build techstack settings UI (codex)

[numnx]

🧩 Task: Build techstack settings UI

Automated task PR opened by Code UX for T02.

📋 Summary

Sprint: Sprint 157 · Techstack Settings + Quickactions for Webapp + Desktop App · Task: T02

Add a system-managed techstack catalog and project techstack selection, expose Settings and navbar controls, and add Create Web App/Create Desktop App quickactions that apply the selected/default techstack only to newly created projects while setup can detect techstacks for imported projects.

📝 Full Task Prompt

## Objective
Expose techstack catalog management in Settings and let operators assign or clear the selected project techstack without affecting imported projects by default.

## Scope
- `dashboard/src/v2/hooks/use-settings-page-state.ts`
- `dashboard/src/v2/components/settings/SettingsCategoryRail.tsx`
- `dashboard/src/v2/components/settings/SettingsContentPanels.tsx`
- `dashboard/src/v2/components/settings/panels/SettingsTechstacksPanel.tsx` (new)
- `dashboard/src/v2/lib/settings-search-index.ts`
- `dashboard/src/v2/components/settings/__tests__/SettingsControls.test.tsx`
- `tests/dashboard/lib/settings-search-index.test.ts`
- `docs/dashboard/design-system-settings.md`
- `docs/settings/subcategories/index.md`
- `docs/settings/subcategories/techstacks.md` (new)
- `docs-web/user/dashboard/settings.md`

## Implementation Requirements
1. Add a `techstacks` settings category and route it through `SettingsContentPanels` to a new `SettingsTechstacksPanel`.
2. In system scope, render the catalog with create/edit/remove controls for non-built-in stacks, default-stack selection, tech item editing, inline validation for id/name/items, and duplicate-action suppression while saving.
3. In project scope, render a project techstack selector with explicit `Unassigned` support, a desktop/web application-kind selector, and clear messaging that imported projects remain unassigned until selected or setup detects one.
4. Use existing `SectionCard`, `Row`, form controls, `ActionFeedbackRegion`, and settings badge helpers so inherited/project-overridden state follows current Settings behavior.
5. Add Smart Find terms for techstack, stack, Preact, TanStack Router, GSAP, Three.js, Lucide, web app, desktop app, and package scan.
6. Add focused tests for category rendering, search discoverability, built-in stack non-removability, project unassigned selection, and project assignment persistence through the settings state helpers.
7. Add the new subcategory docs page and mirror public Settings documentation with the user-facing workflow.

## Constraints
- Do not edit navbar quickactions or project creation flows in this task.
- Do not allow deletion of the built-in internal techstack.
- Keep dense settings layouts responsive with `minmax(min(100%, ...), 1fr)` patterns where grids are introduced.
- Preserve existing settings category keyboard behavior and `aria-current`/`aria-selected` semantics.

## Verification
- Run `pnpm exec vitest run dashboard/src/v2/components/settings/__tests__/SettingsControls.test.tsx tests/dashboard/lib/settings-search-index.test.ts`.
- Run `pnpm run test:dashboard` if shared settings components are changed.
- Success means the Settings page exposes a searchable Techstacks category, built-in stack controls are protected, and project selection can be set or cleared without layout or accessibility regressions.

✅ QA Review

⏳ QA review runs after this PR is opened. Check the task card in the dashboard for the outcome once it lands.

🤖 Model & Provider

Provider	Codex CLI
Model	gpt-5.5

⏱️ Timing

Started	2026-07-07 04:33:27 UTC
Finished	2026-07-07 04:44:49 UTC
Duration	11m 22s

📊 Token Usage

Metric	Value
Input tokens	168,708
Cached input tokens	4,722,816
Output tokens	23,206
Total tokens	4,914,730
Invocations	1
Tool calls	73
Active time	10m 49s

Included usage estimate (subscription/local login): $3.90

🌿 Branch Info

Base: feature/CODUX-157-techstack-settings-quickactions-for-webapp-desktop-app
Head: task/feature-codux-157-techstack-settings-quickaction-t02-codex-mra5ls0y

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🤖 Generated by Code UX