Read the computer's port and timeouts through the fallback the browser limits use

[kevin9327]

What this changes

agent-computer reads PORT, NAVIGATION_TIMEOUT_MS and ACTION_TIMEOUT_MS with
Number.parseInt(process.env.X ?? "default", 10). That is the exact shape #96 removed for the
browser limits: an unset variable declared in a compose file arrives as an empty string, so ??
sees "" rather than undefined, never fires, and Number.parseInt("") is NaN.

ACTION_TIMEOUT_MS is a documented variable (.env.example:173), so a deployment that sets it the
way the compose file already sets COMPUTER_MAX_BROWSERS/COMPUTER_BROWSER_IDLE_MS (${VAR:-})
hands Playwright a NaN timeout instead of the 10s the default promises — a computer that looks
broken rather than misconfigured, which is precisely the failure #96 wrote up.

The fix reuses #96's own helper: numberFromEnv (empty, absent, non-numeric and non-positive all
take the fallback) is exported from profiles.ts and the three values are read through it, so the
whole package treats a bad or empty timeout the same way it already treats a bad or empty browser
cap.

Where it runs

• New state that outlives a request? None. Three module constants read once at startup.
• What happens on the second replica? Identical to the first — this is per-process config,
  not shared state. The change is that an empty or malformed value now yields the default on
  every replica instead of NaN.
• Anything serialised / fanned out / new listener? No. No schema, socket, port or schedule
  changes; the port number is parsed more safely but the listener is the same one.

Boundary and audit

• No acting call, policy decision or audit path is touched. This is startup configuration for the
  computer process's own timeouts and port.

Proof

agent-computer is not reached by the root typecheck (that gap is filed as #112), so verified in
the package directly:

• bunx tsc --noEmit — clean.
• bun test tests/number-from-env.test.ts — 5/5. New test covers a positive value (trimmed), unset,
  the empty string a compose file passes for an unset variable, a non-numeric value, and
  zero/negative — each of the last four taking the fallback.

Self-contained: numberFromEnv already existed and is unchanged in behaviour; this only exports it
and moves three neighbours onto it.

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[davidmckayv]

The fix is right and low-risk — a declared-but-empty compose var arrives as "", Number.parseInt("") is NaN, and routing PORT and the two timeouts through the existing numberFromEnv matches what #96 did for the browser limits. It merges clean against main. But it ships CI red, and that's the blocker.

agent-computer/tests/number-from-env.test.ts:2 imports numberFromEnv from ../src/profiles, and agent-computer/src/profiles.ts:38 hard-imports playwright at module load. The test runner can't resolve playwright there, so the test file throws on import — Cannot find package 'playwright' — which drops the file's tests and fails both the tests job and verify.

The move: put numberFromEnv in its own tiny playwright-free module (e.g. agent-computer/src/env.ts), re-export it from profiles.ts so nothing else changes, and import it in the test from there. Then CI goes green and this is a merge.