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.

package.json

@@ -148,7 +148,7 @@
     "release:verify-packed-install": "tsx scripts/release/verify-packed-install.ts",
     "release:publish": "tsx scripts/release/publish.ts",
     "dsh": "node --import tsx/esm apps/cli/src/bin.ts",
-    "demo:code-mode": "node scripts/demo-code-mode.mjs",
+    "demo:ptc": "node scripts/demo-ptc.mjs",
     "demo:inspector": "node --import tsx/esm apps/cli/src/bin.ts web --patch ./packages/experimental/inspector/cordis.source.patch.yml",
     "mock:llm": "node --import tsx packages/test-support/llm-mock-server/src/bin.ts",
     "dev:web": "tsx scripts/dev-web.ts --poll",