fix(setup)!: bind managed registrations to selected installation

Use one command owner for setup, client writers, Gemini policy and CLI defaults.
Migrate recognized runner registrations with backups and remove runner prewarm.
Retain unknown identities and exercise real offline npm, CLI and MCP workflows.

Fixes #7757

BREAKING CHANGE: managed MCP registrations use the selected absolute runtime
and REA entry script, including package-runner cache paths. Keep that installation
available or restore it before setup; unknown registrations require confirmed
manual repair. Setup no longer returns prewarm or emits its progress events.

Assisted-by: Reimu (gensokyo-skills:reimu-incident-triage)
Assisted-by: Kogasa (gensokyo-skills:kogasa-surprise-testing)
Assisted-by: Yukari (gensokyo-skills:yukari-boundary-analysis)

src/cli/clientRegistrationCommandText.ts

@@ -0,0 +1,5 @@
+/** Incur takes a command string and splits quoted segments without backslash escapes. */
+export const clientRegistrationCommandText = (
+  command: readonly string[],
+): string =>
+  command.map((argument) => `'${argument.replaceAll("'", `'"'"'`)}'`).join(" ");