rename code-mode to ptc (PTC mode), except session-persistent vocabulary

Rename the tool-presentation transport from code-mode to ptc everywhere
that is not written into session logs: the mode config value becomes 'ptc',
the preset directory/id becomes ptc, the demo becomes demo:ptc, the
dispatch waterfall becomes tools/ptc-dispatch-log (types PtcDispatch*), the
prompt rule becomes tools:ptc-only, source/test files become ptc.ts etc.,
and prose says PTC mode / PTC 模式. The session-persistent vocabulary
(durable events tool/code-dispatch*, logged plugin name tools-code-mode,
sub-call id segment :code:) intentionally stays and moves in the stacked
persistence PR, which is blocked until the SESSION_FORMAT_VERSION v0→v1
migration lands with it. run_code, its code parameter, CodeSdkLanguage,
CodeRunFailedError, the dsh-code-runtime family, third-party codex names,
and frozen archived notes keep their names.

tsconfig.host.json

@@ -46,7 +46,7 @@
     "apps/web/tests/sidebar-scrollbar.e2e.ts",
     "apps/web/tests/rail-search-expand.e2e.ts",
     "apps/web/tests/conversation-column-overflow.e2e.ts",
-    "apps/web/tests/code-mode-round.e2e.ts",
+    "apps/web/tests/ptc-round.e2e.ts",
     "apps/web/tests/composer-draft-scroll.e2e.ts",
     "apps/web/tests/cordis-tool-round.e2e.ts",
     "apps/web/tests/web-search-round.e2e.ts",