feat: add configurable worktree project mappings (#481)

Closes #416.

Adds user-configurable rules that map worktree paths back to a canonical
project, so worktree sessions group with the parent repo instead of
becoming
a separate project derived from the branch name.

The built-in parser infers a session's project from its `cwd`, which
works for
standard layouts but not custom worktree conventions like
`~/code/{project}.worktrees/feat/my-feature/` — those sessions end up
under
`my-feature` rather than `{project}`. This branch adds a manual override
that
lives in SQLite, is scoped to the current machine, and is applied both
as new
sessions stream in and to existing sessions on demand.

## How it works

- New `worktree_project_mappings` table keyed by `(machine,
path_prefix)` with
an `enabled` flag. Path prefixes are cleaned and have trailing
separators
stripped so matches are stable regardless of how a user types the
prefix.
- The sync engine loads the active mappings for the host machine on each
pass
and rewrites `project` for any session whose `cwd` falls under an
enabled
  prefix. The resolver is wired into all ingestion paths: single-session
  writes, incremental sync, bulk resync, and the rebuild-and-swap full
resync. Excluded, trashed, and skipped session files are left alone so
the
  rewriter does not resurrect intentionally removed data.
- REST API under `/api/v1/settings/worktree-mappings` (list / create /
update /
delete / apply). The server derives the machine identifier itself
instead
of accepting it from the client, so a mapping created on one machine
never
  bleeds into another machine's view of synced sessions.
- Settings panel in the SPA for adding, editing, toggling, and deleting
mappings, plus an Apply action that runs the rewrite over
already-imported
  sessions and reports how many were matched and updated.

## Notes

- Mappings are explicit and manual — there is no auto-discovery. The
intent
is to let users formalize their personal layout once and have it stick.
- Mappings only mutate `project`; the rest of the session record,
including
data carried through the bulk resync's rebuild-and-copy path, is
preserved.

---------

Co-authored-by: OpenAI Codex <noreply@openai.com>
Co-authored-by: Wes McKinney <wesmckinn+git@gmail.com>

Author: 3 people

frontend/src/lib/api/client.ts

@@ -813,6 +813,75 @@ export function updateSettings(
   });
 }
 
+export interface WorktreeProjectMapping {
+  id: number;
+  machine: string;
+  path_prefix: string;
+  project: string;
+  enabled: boolean;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface WorktreeMappingsResponse {
+  machine: string;
+  mappings: WorktreeProjectMapping[];
+}
+
+export interface WorktreeMappingInput {
+  path_prefix: string;
+  project: string;
+  enabled: boolean;
+}
+
+export interface ApplyWorktreeMappingsResponse {
+  machine: string;
+  matched_sessions: number;
+  updated_sessions: number;
+}
+
+export function getWorktreeMappings(): Promise<WorktreeMappingsResponse> {
+  return fetchJSON("/settings/worktree-mappings");
+}
+
+export function createWorktreeMapping(
+  input: WorktreeMappingInput,
+): Promise<WorktreeProjectMapping> {
+  return fetchJSON("/settings/worktree-mappings", {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(input),
+  });
+}
+
+export function updateWorktreeMapping(
+  id: number,
+  input: WorktreeMappingInput,
+): Promise<WorktreeProjectMapping> {
+  return fetchJSON(`/settings/worktree-mappings/${id}`, {
+    method: "PUT",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(input),
+  });
+}
+
+export async function deleteWorktreeMapping(id: number): Promise<void> {
+  const res = await fetch(
+    `${getBase()}/settings/worktree-mappings/${id}`,
+    authHeaders({ method: "DELETE" }),
+  );
+  if (!res.ok) {
+    const body = await res.text();
+    throw new ApiError(res.status, apiErrorMessage(res.status, body));
+  }
+}
+
+export function applyWorktreeMappings(): Promise<ApplyWorktreeMappingsResponse> {
+  return fetchJSON("/settings/worktree-mappings/apply", {
+    method: "POST",
+  });
+}
+
 /* Analytics */
 
 export interface AnalyticsParams {

frontend/src/lib/components/settings/SettingsPage.svelte

@@ -8,6 +8,7 @@
   import TerminalSettings from "./TerminalSettings.svelte";
   import GithubSettings from "./GithubSettings.svelte";
   import RemoteSettings from "./RemoteSettings.svelte";
+  import WorktreeMappingSettings from "./WorktreeMappingSettings.svelte";
 
   let authTokenInput: string = $state("");
 
@@ -87,6 +88,7 @@
       <AppearanceSettings />
       <AgentDirSettings />
       <TerminalSettings />
+      <WorktreeMappingSettings />
       <GithubSettings />
       <RemoteSettings />