feat(PRLT-1369): support multiple Claude accounts via --executor-env / --executor-bin

[chrismcdermut]

Summary

• Adds two new flags to all spawn-style commands that let users point a spawned executor at a different Claude account or wrap it with a custom binary, without changing the executor type:
  • --executor-env KEY=VALUE (repeatable) — sets env vars on the spawned executor (e.g. CLAUDE_CONFIG_DIR=$HOME/.claude-work to switch accounts).
  • --executor-bin <path> — overrides the executor binary (e.g. an absolute path or wrapper script).
• Wired through work start, work spawn, work run, orchestrator start, claude, qa, and agent shell.
• Threaded into runners: host (export lines in tmux script), devcontainer (docker exec -e KEY=VALUE), docker (docker run -e), cloud (env prefix on remote ssh command), and the inline agent shell claude/docker exec.
• Backward compatible — omitting the flags behaves exactly as before.

Implementation notes

• New helper module apps/cli/src/lib/execution/executor-overrides.ts with: parseExecutorEnv, buildShellExports, buildDockerEnvFlags, executorOverrideFlags, readExecutorOverridesFromFlags. Single source of truth for parsing/escaping.
• getExecutorCommand gained an optional 4th binOverride arg so all runners can swap the binary uniformly. 'custom' executor with --executor-bin finally produces a real command instead of the echo fallback.
• ExecutionContext and SpawnOptions extended with executorEnv?: Record<string, string> and executorBin?: string. Runners read them off the context — no new arguments to the dispatcher.

Test plan

• New unit tests in apps/cli/test/unit/executor-overrides.test.ts (22 tests) covering parser, shell/docker fragment builders, flag reader, and getExecutorCommand binOverride paths
• Existing executor command suite (31 tests) still passes
• pnpm build clean
• Manual verification: `prlt work start --executor-env CLAUDE_CONFIG_DIR=$HOME/.claude-work` spawns an agent against the alternate account
• Manual verification: same flag works on a devcontainer agent (env var set inside container via `docker exec -e`)

🤖 Generated with Claude Code