fix(agent): semantic_search symbol index workspace-aware

SymbolIndex global sudah melacak workspace_path tapi SemanticSearch dan
ListSymbols Cuma rebuild saat index kosong (is_empty). Akibat: setelah
mengindeks workspace A, mencari di workspace B diam-diam mengembalikan
simbol STALE dari A — menyesatkan coding agent (referensikan simbol yang
tidak ada di repo aktif).

Fix:
- Tambah SymbolIndex::needs_rebuild(workspace) — true bila index kosong
  ATAU workspace diminta beda dari yang ter-cache.
- Pakai di 2 call site (SemanticSearch::run, ListSymbols::run) menggantikan
  is_empty(), jadi pindah workspace otomatis trigger rebuild.
- test: +1 (test_needs_rebuild_workspace_aware — verifikasi flip workspace
  memicu rebuild bolak-balik A -> B -> A).

Catatan (bukan bug, dilaporkan): mutex SYMBOL_INDEX masih dipegang selama
full rebuild di run() — bottleneck saat semantic_search dipanggil paralel;
perbaikan butuh restrukturisasi double-checked rebuild, tak diubah di sini.

Verifikasi: check/clippy -D warnings/fmt clean; test infra 63 (0 gagal).

Cargo.lock

@@ -4862,7 +4862,7 @@ dependencies = [
 
 [[package]]
 name = "zesdex-api"
-version = "1.20.1"
+version = "1.20.2"
 dependencies = [
  "anyhow",
  "argon2",
@@ -4885,7 +4885,7 @@ dependencies = [
 
 [[package]]
 name = "zesdex-application"
-version = "1.20.1"
+version = "1.20.2"
 dependencies = [
  "anyhow",
  "base64",
@@ -4903,7 +4903,7 @@ dependencies = [
 
 [[package]]
 name = "zesdex-bootstrap"
-version = "1.20.1"
+version = "1.20.2"
 dependencies = [
  "anyhow",
  "chrono",
@@ -4920,7 +4920,7 @@ dependencies = [
 
 [[package]]
 name = "zesdex-daemon"
-version = "1.20.1"
+version = "1.20.2"
 dependencies = [
  "anyhow",
  "base64",
@@ -4944,7 +4944,7 @@ dependencies = [
 
 [[package]]
 name = "zesdex-domain"
-version = "1.20.1"
+version = "1.20.2"
 dependencies = [
  "anyhow",
  "base64",
@@ -4960,7 +4960,7 @@ dependencies = [
 
 [[package]]
 name = "zesdex-gateway"
-version = "1.20.1"
+version = "1.20.2"
 dependencies = [
  "anyhow",
  "axum",
@@ -4987,7 +4987,7 @@ dependencies = [
 
 [[package]]
 name = "zesdex-grpc"
-version = "1.20.1"
+version = "1.20.2"
 dependencies = [
  "anyhow",
  "axum",
@@ -5004,7 +5004,7 @@ dependencies = [
 
 [[package]]
 name = "zesdex-infrastructure"
-version = "1.20.1"
+version = "1.20.2"
 dependencies = [
  "anyhow",
  "argon2",
@@ -5052,7 +5052,7 @@ dependencies = [
 
 [[package]]
 name = "zesdex-tui"
-version = "1.20.1"
+version = "1.20.2"
 dependencies = [
  "anyhow",
  "base64",
@@ -5078,7 +5078,7 @@ dependencies = [
 
 [[package]]
 name = "zesdex-web"
-version = "1.20.1"
+version = "1.20.2"
 dependencies = [
  "anyhow",
  "axum",
@@ -5098,7 +5098,7 @@ dependencies = [
 
 [[package]]
 name = "zesdex-ws"
-version = "1.20.1"
+version = "1.20.2"
 dependencies = [
  "anyhow",
  "axum",