test(core): vim idle regression + drop interactive CPU/fuel overrides

[NathanFlurry]

• Remove the interactive-shell AGENTOS_V8_CPU_TIME_LIMIT_MS and 24h maxWasmFuel overrides — idle interactive guests no longer burn the default watchdogs after the secure-exec event-driven kernel-wait servicing, so the defaults are correct as-is. Requires the next secure-exec pin bump to include those runtime fixes.
• Remove the same CPU override from the brush-interactive test.
• Parameterize the vim test fixture and snapshot paths with env overrides (AGENTOS_VIM_FIXTURE_DIR, AGENTOS_VIM_SNAPSHOT_DIR) so the suites are not tied to one machine's layout.
• Add an idle regression test: a raw-mode full-screen vim idles 60s+ on default limits and still consumes keystrokes afterwards.