[process-manager PM-5] Process runner: Deno.Command-native spawn + descendant-tree kill

[rickylabs]

Summary

Lean Deno.Command-native process runner (no dax): RuntimeCommandSpec + argv builders, buildEnvironment() trace injection (TRACEPARENT), TextLineStream output handling, and a correct descendant-tree kill (POSIX process-tree walk / Windows taskkill /T) — fixing pup's unfixed descendant-kill bug class.

Scope

• Archetype / area: packages/plugin-process-manager-core engine
• Part of Epic: NetScript Process Manager — bare-metal supervisor + admin console (pup/pm2 done right) #510
• Depends on: [process-manager PM-1] Process-graph contract v1 (ProcessGraphShape/ProcessSpecShape + state vocabulary + restart policies) #512 · Blocks: PM-6, PM-7

Design source

• research/design/d1-supervision-engine-core.md (D1-S4 + D1-S5) · plan.md §4 PM-5

Acceptance criteria

• gate: spawn/stream/kill covered by tests incl. a descendant-tree kill test on both platforms' code paths
• gate: no dax / no @std/io deprecated APIs — Web Platform + Deno.* only
• gate: TRACEPARENT env injection present and tested
• gate: scoped check/lint/fmt wrappers green (--ext ts,tsx)

Non-scope

• Restart policy (PM-4); log persistence (PM-7).

Drift / Debt

• none

RFC #820 amendment (owner-ratified 2026-07-17 — PR #822)

• gate: spawn supports clearEnv + a documented runtime-inherited strip list (DENO_* incl. DENO_SERVE_ADDRESS, NODE_CHANNEL_FD) for compiled/desktop hosts (Deno ≥ 2.9.3, BUG: deno compile on Windows: child_process.spawn with extra stdio pipe fds fails intermittently with "The handle is invalid. (os error 6)" denoland/deno#35994). PUBLIC additive RuntimeCommandSpec extension — jsr rubric + consumer-compile gate.