Make test suite runnable from clean checkout + cross-platform vram_detect

runnable-test-suite (parent) — complete. Three sub-tasks all complete:

- make-tests-runnable: add requirements.txt pinning pytest==7.4.4, sweep all
  docs/prompts from bare 'python' to 'python3' (stock macOS/Windows ships
  python3), add idempotent .venv install block to scripts/install.sh, and add
  'from __future__ import annotations' to 3 dashboard modules using PEP 604
  union syntax at definition time so they import on Python 3.9+. The
  PEP 604 bug was caught by the streak verifier itself during implementation.

- vram-detect-cross-platform: scripts/vram_detect.py now branches on
  platform.system() for Linux/Darwin/Windows. macOS path uses
  system_profiler SPDisplaysDataType (Apple Silicon unified memory via
  sysctl hw.memsize; Intel Macs via 'VRAM (Total):'). Windows uses wmic
  path win32_VideoController get AdapterRAM with PowerShell fallback. Linux
  /proc/meminfo and nvidia-smi/lspci paths unchanged (regression test locks
  them). Added 14 local-LLM context-window entries (llama-3.1, qwen2.5,
  mistral, deepseek-r1/v3, glm-4/4.5, gemma-2, phi-3/4) with source-cited
  model cards. Added _probe_ollama_model() that runs 'ollama list' as a
  last-resort fallback. run_command() now wraps PowerShell cmdlets on
  Windows (['powershell', '-NoProfile', '-NoLogo', '-Command', ...]).

- vram-detect-cross-platform-tests: 11 new monkeypatched tests in
  tests/test_vram_detect.py covering Linux/Darwin/Windows branches for
  detect_ram and detect_gpu_vram, prefix-match for unknown model names,
  ollama probe, Windows PowerShell wrapper, and a LOCKED regression test
  for _detect_ram_linux(). All external subprocess/sysctl/wmic calls are
  mocked; no live hardware probes. Suite total: 235 passed, 0 errors.

Verified on this box: gpu_vram_gb 0 -> 32 on Apple M5 (32GB unified memory),
target context correctly jumped 12k -> 42k.

Subtask-2 implementation was authored by local LLM (gemma-4-26B-A4B-it
via headroom proxy @ localhost:8787). The 10-consecutive-clean-pass streak
verifier ran as the independent checker model (article #2/#9/#13 in
'WTF Is a Loop? Part 2'). One anti-spin rail fired: local LLM produced
inline branches where subtask-3 tests expected private _detect_ram_linux()
helper; extracted helper to match the test contract without weakening tests.

Parent + all 3 subtasks complete. Prior opencode-subagent implementation
of subtask-2 preserved in git stash for reference.

CHANGELOG.md

@@ -3,6 +3,8 @@
 ## [unreleased]
 
 ### Added
+- **Added:** `requirements.txt` pinning `pytest==7.4.4` for reproducible test runs.
+- **Added:** `scripts/install.sh` now creates `.venv/` and installs pytest into it.
 - **Harness pre-edit hook**: `--can-edit` now supports project-level checks without `--task`, file scope checks with `--file`, and `--json` output for machine-readable harness integration
 - **opencode plugin**: `plugins/automaton-guard/plugin.ts` — intercepts `edit` and `write` tool calls, calls `--can-edit` before allowing modifications
 - **Git pre-commit hook**: `scripts/git-hooks/pre-commit` — blocks commits when no task is in an edit-allowed phase (universal safety net for all harnesses)
@@ -34,6 +36,7 @@
 - **Framework version marker**: `config.md` now includes version 2.0 with state enforcement indicator
 
 ### Changed
+- **Changed:** All documented `python` invocations now read `python3` (stock macOS / Windows Python ship as `python3`).
 - **orchestrate.md**: Reduced from 493 to 143 lines; gate-check loop replaces soft advisory approach; approval gates enforced at research, decomposition, design, and test_design
 - **workflow.md**: Rewritten to reference `.state` as canonical phase indicator; approval sub-states documented; enforcement via `status.py` documented
 - **All phase prompts**: Added `.state` precondition check, pre-work validation, ALLOWED/FORBIDDEN sections, handling user overrides