v1.9: settings pane + per-project defaults + bulk archive + themes lift

Adds a singleton, ephemeral 'settings' pane kind to the workspace.
Opened via a new bottom-pinned button in ProjectSidebar (emits an
open_settings_pane event when a session is mounted; navigates to
/settings otherwise). Pane has three sections — Session, Project,
Theme — and a maximize toggle that hides sibling pane columns via
display:none on desktop only. Settings panes don't count toward
MAX_PANES and are filtered out of the localStorage persistence layer
so reload always restores a clean workspace.

Schema (additive):
- projects.default_system_prompt TEXT NOT NULL DEFAULT ''
- projects.default_web_search_enabled BOOLEAN NOT NULL DEFAULT false
- sessions.web_search_enabled BOOLEAN  (nullable; null = inherit)

Inference resolves user_prompt = session.system_prompt.trim() ||
project.default_system_prompt.trim() — empty/whitespace at either
layer means "no override". Keeps the columns NOT NULL and matches
the existing inherit semantics.

Server routes:
- GET /api/projects/:id (new; settings pane refetches on
  project_updated)
- PATCH /api/projects/:id accepts default_system_prompt,
  default_web_search_enabled
- PATCH /api/sessions/:id accepts web_search_enabled (tri-state)
- POST /api/projects/:id/sessions/archive-all + GET
  /api/projects/:id/sessions/open-count
- POST /api/sessions/:id/chats/archive-all + GET
  /api/sessions/:id/chats/open-count
- PATCH /api/sessions/:id now broadcasts session_updated on every
  successful PATCH (was rename-only). Lets SettingsPane open in
  another tab pick up edits without a refetch.

Bulk-archive publishes one session_archived / chat_archived frame
per affected id so useSidebar's existing reducer cases handle them
incrementally — no new frame type, no payload widening.

ModelPicker refactored: shared ModelList inside a responsive shell.
Desktop = labeled trigger + DropdownMenu, mobile = icon-only Cpu
button + BottomSheet. Header in Session.tsx drops the pill wrap on
mobile since the new trigger is the visual.

ChatInput gains an icon-only '+' DropdownMenu next to AgentPicker
when sessionId + webSearchEnabled props are provided. One item for
now — Web search — with a checkmark reflecting the stored value
(true), not the effective one. Click PATCHes the override; to
restore inherit-from-project the user opens SettingsPane.

ThemePicker lifted out of pages/Settings.tsx into a reusable
component. The standalone /settings route is now a thin wrapper
that mounts <ThemePicker /> with a Back button on top
(navigate(-1) with fallback to '/'); the SettingsPane Theme tab
renders the same picker bare.

Project section delete-flow removed (button + confirm dialog +
handler). Replaced with "Archive all sessions" using the same
two-step count → confirm → fire pattern as "Archive all chats" in
the Session section. api.projects.remove() stays in the client
because useProjects.ts still uses it.

Hand-rolled Switch primitive in SettingsPane (no shadcn switch in
the project; spec said no new deps). Section nav is plain buttons
(no shadcn Tabs).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/server/src/services/inference.ts

@@ -149,9 +149,11 @@ export interface InferenceContext {
   publishUser: (frame: UserStreamFrame) => void;
 }
 
-// Resolution order: base prompt < agent.system_prompt < session.system_prompt.
-// Agent prompts layer on top of the base; session prompt is the most specific
-// override and stacks last so callers can append per-session instructions.
+// Resolution order: base prompt < agent.system_prompt < user prompt, where
+// user prompt = session.system_prompt if non-empty, else project's
+// default_system_prompt if non-empty, else nothing. Empty/whitespace-only
+// counts as "no override" for both layers (v1.9 inherit semantics — keeps
+// the column non-nullable so the existing key/value store stays put).
 export function buildSystemPrompt(
   project: Project,
   session: Session,
@@ -161,8 +163,11 @@ export function buildSystemPrompt(
   if (agent && agent.system_prompt.trim().length > 0) {
     out += '\n\n' + agent.system_prompt.trim();
   }
-  if (session.system_prompt && session.system_prompt.trim().length > 0) {
-    out += '\n\n' + session.system_prompt.trim();
+  const sessionPrompt = session.system_prompt?.trim() ?? '';
+  const projectPrompt = project.default_system_prompt?.trim() ?? '';
+  const userPrompt = sessionPrompt || projectPrompt;
+  if (userPrompt.length > 0) {
+    out += '\n\n' + userPrompt;
   }
   return out;
 }
@@ -240,14 +245,16 @@ async function loadContext(
   chatId: string
 ): Promise<{ session: Session; project: Project; history: Message[] } | null> {
   const sessionRows = await sql<Session[]>`
-    SELECT id, project_id, name, model, system_prompt, status, created_at, updated_at, agent_id
+    SELECT id, project_id, name, model, system_prompt, status, created_at, updated_at,
+           agent_id, web_search_enabled
     FROM sessions WHERE id = ${sessionId}
   `;
   if (sessionRows.length === 0) return null;
   const session = sessionRows[0]!;
 
   const projectRows = await sql<Project[]>`
-    SELECT id, name, path, added_at, last_session_id
+    SELECT id, name, path, added_at, last_session_id, status, gitea_remote,
+           default_system_prompt, default_web_search_enabled
     FROM projects WHERE id = ${session.project_id}
   `;
   if (projectRows.length === 0) return null;