feat(supervisor): single-declaration baseSpawnEnv for every agent CLI spawn

[SDSLeon]

Summary

Introduces baseSpawnEnv as the single declaration point for env that must ride every Poracode-made spawn of an agent CLI, replacing per-command-builder env duplication. In practice this is for CLIs that fire a detached background self-updater — on Windows that updater escapes its parent's pseudoconsole, allocates a fresh console, and (with Windows Terminal as the default terminal app) pops a stray terminal window mid-session.

A provider now declares its opt-out once on the DetectionSpec; shared runtime fans it out to every lane, so a new launch point picks it up for free instead of every command builder having to remember its own env.

Changes

• base/spawnEnv.ts (new) — mergeSpawnEnv, withCommandBaseSpawnEnv, withBaseSpawnEnv, inheritBaseSpawnEnv. Adapters derive the map from their spec via ...inheritBaseSpawnEnv(spec) so the two can never drift.
• Lane fan-out — detection probes (merged under probeEnv), terminal login (via authMethods[].env), PTY launch, ACP session/auth/logout, one-shots, context extraction, and subagent children.
• update stays exempt — the user-driven "update agent" action must still reach the CLI's own updater.
• New: antigravity AGY_CLI_DISABLE_AUTO_UPDATE — including the account probe, whose 5-minute TTL was exactly the cadence that kept re-arming the updater.
• Migrated to baseSpawnEnv — commandcode, factory, and muse drop their repeated per-builder env.
• Cache invalidation — STATUS_CACHE_VERSION 13→14 and the renderer store 10→11, since terminal auth methods now carry baseSpawnEnv-derived env; a status persisted before that derivation would build a login command without it.

Review fixes folded in

• SubagentAttemptRunner built a CreateStructuredSessionInput by hand and never passed baseSpawnEnv, unlike SpawnPipeline — the one launch point where the "can't silently miss it" guarantee wasn't holding. Pinned with two regression tests.
• buildFactoryCommand's env parameter replaced the base constant instead of layering on top, so a caller forwarding a narrower env would have silently dropped the opt-out out of the WSL login-shell script — the one lane where spawn-level env can't rescue it. Now merges.
• withCommandBaseSpawnEnv is generic over the command shape, so lane extras (stdin, isolateCwd) survive the wrap.

Testing

• pnpm run typecheck, pnpm run lint, pnpm run fmt:check — all pass.
• pnpm exec vitest run src/supervisor src/renderer/state — 4098 passed, 1 failed. The single failure is the pre-existing gemini/plugin/install.test.ts pwsh-absolute-path assertion, in a file this branch does not touch.
• Verified AGY_CLI_DISABLE_AUTO_UPDATE is a real string in the shipped agy.exe (adjacent to failed to check for updates), so the new opt-out is not a guess.

🤖 Generated with Claude Code