feat(ui): replace Settings stub with screen matching Figma node 17:2

[ilmoniemi]

User Story

As a Pyrycode mobile user opening Settings, I want a structured sectioned screen matching the locked Figma design, so I can see the canonical settings categories (Connection, Appearance, Defaults, Notifications, Memory, Storage, About) with the correct row types instead of a placeholder.

Context

Phase 1's #16 wired a Settings route, but the destination is a literal SettingsPlaceholder composable with the text "Settings placeholder" + Back button. Figma node 17:2 shows the canonical full-screen sectioned settings layout.

This ticket builds the visual skeleton — sections + section headers + row stubs with the correct trailing affordances. Wiring each row's destination, persisting toggle state, and showing real values are Phase 3+ tickets; this ticket lands the visual structure only, with placeholder literals matching Figma.

Acceptance Criteria

• New composable SettingsScreen at app/src/main/java/de/pyryco/mobile/ui/settings/SettingsScreen.kt replaces the SettingsPlaceholder stub; MainActivity.kt Routes.Settings composable invokes the new screen and the old SettingsPlaceholder private composable is removed.
• Screen renders M3 TopAppBar with title "Settings" and a back navigation icon that calls the existing onBack (already wired via the NavHost).
• Body is a vertically scrollable list with the following sections in this order, each preceded by an M3 section header (label-style, indented to match Figma):
  1. Connection — rows: Server (subtitle placeholder "juhana-mac-2026", trailing chevron); Pair another server (single-line, trailing chevron).
  2. Appearance — rows: Theme (subtitle "System", trailing chevron); Use Material You dynamic color (single-line, trailing M3 Switch).
  3. Defaults for new conversations — rows: Default model (subtitle "Opus 4.7", chevron); Default effort (subtitle "high", chevron); Default YOLO (subtitle "off", trailing Switch); Default workspace (subtitle "scratch", chevron).
  4. Notifications — rows: Push notifications when claude responds (single-line, trailing Switch); Notification sound (subtitle "Default", chevron).
  5. Memory — rows: Installed memory plugins (subtitle "0 plugins", trailing outlined Add button with leading plus icon); Manage per-channel memory (single-line, chevron).
  6. Storage — rows: Archived conversations (subtitle "11 archived", chevron); Clear cache (single-line, chevron).
  7. About — rows: Version 0.1.0 (subtitle "build a8f3c2d", no trailing affordance); Open source · github.com/pyrycode/pyrycode-mobile (trailing external-link icon, two-line wrap allowed); Privacy policy (single-line, trailing external-link icon); License: MIT (single-line, no trailing affordance).
• Switch rows hold local-only state (remember { mutableStateOf(...) } with defaults matching Figma: Material You = on, Default YOLO = off, Push notifications = on); no persistence, no ViewModel, no hoisted callbacks — pure visual stub.
• All other row taps and the Add button are no-op (or a Log.d TODO marker); sub-screens land in Phase 3 tickets.
• Zero hardcoded colors / typography / spacing literals — colors come from MaterialTheme.colorScheme, type from MaterialTheme.typography, spacing from M3 defaults (ListItem, dp values matching the 8dp grid are acceptable for section-header padding).
• @Preview for light and dark; both render without crashing and visually match Figma 17:2 structurally (correct sections, correct row count per section, correct trailing affordance per row).

Technical Notes

• Existing stub at MainActivity.kt:175-189 (SettingsPlaceholder composable) — remove after wiring the new screen. Update MainActivity.kt:175 (the composable(Routes.Settings) block) to call SettingsScreen(onBack = { navController.popBackStack() }).
• Prefer M3 ListItem for row primitives; use headlineContent / supportingContent / trailingContent slots. The section header is a Text with MaterialTheme.typography.labelLarge (or whichever M3 token best matches Figma's 14sp/medium label — pick by inspection of the rendered Figma).
• Don't introduce a SettingsViewModel or repository yet — there is no state to manage beyond the three local switches.
• Subtitle literals ("juhana-mac-2026", "Opus 4.7", "11 archived", build hash, etc.) are intentional placeholders; do not wire them to BuildConfig, DataStore, or any data source. They are scaffolding that later phases replace.

Size Estimate

S — one new file (~140 LOC including 2 previews) + ~3 LOC change in MainActivity.kt. Two files touched, ~5 ACs of structural work plus one row-enumeration AC; well inside the S envelope.

Figma

https://www.figma.com/design/g2HIq2UyPhslEoHRokQmHG?node-id=17-2

[ilmoniemi]

🤖 Product Owner — creates structured issues

po agent has completed work on this ticket.

Agent output (click to expand)

Refined #64. Key changes from the prior body:

- **AC #3 expanded** from "every row is title + subtitle + chevron" to an enumerated section-by-section table with the exact Figma row labels + trailing affordance per row (chevron / `Switch` / `Add` button / external-link icon / none). The previous AC would have led the architect to spec a single uniform row type and miss the three switches, the Add button, the external-link icons, and the chevron-less About rows.
- **New switch-state AC** clarifies `remember { mutableStateOf(...) }` only — no ViewModel, no persistence — so the architect doesn't over-design.
- **New "zero hardcoded values" AC** spells out which M3 tokens to use (Figma rule was already implicit; made explicit).
- **Technical Notes** name the M3 `ListItem` slots (`headlineContent` / `supportingContent` / `trailingContent`) and warn against wiring placeholder literals to BuildConfig/DataStore.
- **Size revised to ~140 LOC** (was 80-120) — still S, just a more honest estimate after enumerating the rows.

Not applying `security-sensitive` (pure visual stub, no auth/headers/crypto/untrusted-input surface). `size:s` applied; dispatcher will auto-add `ready:po`.

Ready for human review. Move to the next column when approved.

[ilmoniemi]

🤖 System Architect — defines Go interfaces, data flows, concurrency patterns

architect agent has completed work on this ticket.

Agent output (click to expand)

Spec committed to `feature/64` (commit `a464617`).

**Sizing:** confirmed S — one new file (`ui/settings/SettingsScreen.kt`, ~140 LOC + 2 previews) plus ~3 lines in `MainActivity.kt`. `SettingsPlaceholder` has exactly one caller (codegraph confirmed) so no fan-out. No file-overlap with other in-flight feature branches.

**Key spec decisions** (the developer should follow these rather than re-deriving):
- Public surface is a single `SettingsScreen(onBack, modifier)` — no ViewModel, no state class, no Event sealed type. Keeps Phase-3 splitting cheap.
- M3 `ListItem` as the row primitive; `Column + verticalScroll` over `LazyColumn` (24 fixed heterogeneous items, no recycling benefit).
- Three local `mutableStateOf` switches with AC-specified defaults; deliberately **no** `rememberSaveable` (config-change persistence is Phase 3's job).
- Subtitle literals stay inline (scaffolding); only the title + content-descriptions go through `strings.xml`.
- Verification: two `@Preview`s (light/dark, `widthDp = 412`) + manual `installDebug` walkthrough. No unit tests, no instrumented tests — nothing to assert.
- Three open questions called out for the developer (Open source row wrap; OutlinedButton vs TextButton for the "Add" pill; do **not** wire the Material You switch back into `Theme.kt`).

Ready for human review. Move to the next column when approved.