Make workspace IDs opaque, independent of the filesystem path (#1503)

* Make workspace IDs opaque, independent of the filesystem path

Workspace IDs were the resolved checkout/worktree path, so code could
treat an ID as a path: prefix matching, deriving directories from it,
falling back to a path when a lookup missed. IDs are now opaque -
compared only by exact equality and never used as a path. Anything
path-shaped resolves the workspace record first and reads its cwd.

New workspaces get a generated `wks_` ID; existing path-shaped IDs are
read from disk and never regenerated, so there is no migration and no
change to the wire or persisted schemas. Groundwork for running
multiple workspaces in a single directory.

* Keep attachment scope key stable and align refetch test

The attachment scope key keeps `workspace=` instead of `wsid=` so existing
persisted drafts are not orphaned; the rename was cosmetic. The SDK refetch
test no longer asserts a filter, matching refetch fetching one page and
selecting by id client-side.

* Fix live agent updates in directories without a registered workspace

The opaque-ID work removed buildProjectPlacementForCwd's directory
fallback, so an agent running in a folder with no registered workspace
(e.g. a fresh non-git dir) produced a null placement. forwardAgentUpdate
then threw "Workspace not found", the error was swallowed by its catch,
and no agent_update was emitted — live model/thinking switches and status
updates silently stopped. Caught by the live-preferences e2e suite.

The fallback builds a directory-scoped project placement keyed by the
path. That key is a project grouping key (non-git projects group by
path), not a workspace id, so it stays within the opaque-id rule.

* Always run server worktree archive, even without a resolved workspace

Archiving bailed out entirely when the workspace was not found in the
client store, so a race or stale state could make "archive" do nothing
server-side with only a console.warn. The server archive is keyed by
worktreePath, which is always available, so it now runs regardless; only
the optimistic client-side updates (keyed by workspace id) are gated on
the workspace being resolved.

* Expect a directory-scoped placement for unregistered agent dirs

This unit test asserted the no-placement behavior reverted in the live
agent-update fix, which had broken live model/thinking switching. Update
it to expect the directory-scoped placement now emitted for an agent in a
directory with no registered workspace.

* Fix opaque workspace routing in app E2E

* Preserve workspace IDs during partial bootstrap

* Fix archive flows for opaque workspace IDs

* Stop treating opaque workspace IDs as filesystem paths

Workspace IDs are opaque (wks_<hex>), but several call sites still passed
the id where a directory was expected, which broke those flows for opaque
IDs. The branch switcher sent the id as a cwd to branch/stash/checkout git
operations, and server archive/reconcile cleanup keyed git-watch and
subscription teardown by id, leaking that state.

Git and filesystem operations now take the workspace directory; the opaque
id is used only for identity and cache keys. Archive/reconcile cleanup
routes through a single teardownArchivedWorkspace helper that keeps the key
split explicit: runtime store by id, git watch and subscription by cwd.
Path-derived grouping keys are renamed to directory keys, and the helpers
are split into workspace-identity and workspace-directory so the id-vs-path
boundary is obvious.

packages/app/src/utils/host-routes.ts

@@ -100,6 +100,19 @@ function isLegacyPathLikeWorkspaceValue(value: string): boolean {
   return value.includes("/") || value.includes("\\") || /^[A-Za-z]:[\\/]/.test(value);
 }
 
+function hasLegacyDecodeNoise(value: string): boolean {
+  for (const character of value) {
+    const codePoint = character.codePointAt(0);
+    if (codePoint == null) continue;
+    if (codePoint < 0x20 || codePoint === 0x7f || codePoint === 0xfffd) return true;
+  }
+  return false;
+}
+
+function isCleanLegacyPathDecode(value: string): boolean {
+  return isLegacyPathLikeWorkspaceValue(value) && !hasLegacyDecodeNoise(value);
+}
+
 export type WorkspaceOpenIntent =
   | { kind: "agent"; agentId: string }
   | { kind: "terminal"; terminalId: string }
@@ -193,13 +206,14 @@ export function decodeWorkspaceIdFromPathSegment(workspaceIdSegment: string): st
     return prefixedDecoded ? normalizeWorkspaceId(prefixedDecoded) : null;
   }
 
+  // COMPAT(legacyPathWorkspaceId): IDs were path-shaped before v0.1.95. Remove when deep-link floor >= v0.2.0.
   const base64Decoded = tryDecodeBase64UrlNoPadUtf8(decoded);
-  if (base64Decoded && isLegacyPathLikeWorkspaceValue(base64Decoded)) {
+  if (base64Decoded && isCleanLegacyPathDecode(base64Decoded)) {
     return normalizeWorkspaceId(base64Decoded);
   }
 
   const relaxedBase64Decoded = decodeBase64UrlNoPadUtf8(decoded);
-  if (relaxedBase64Decoded && isLegacyPathLikeWorkspaceValue(relaxedBase64Decoded)) {
+  if (relaxedBase64Decoded && isCleanLegacyPathDecode(relaxedBase64Decoded)) {
     return normalizeWorkspaceId(relaxedBase64Decoded);
   }