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.

README.md

@@ -200,34 +200,34 @@ Automaton v2.0 enforces the state machine computationally, not just via prompts:
 
 ```bash
 # Create a new task
-python ~/.automaton/scripts/status.py --create-task add-user-auth --project /path/to/project
+python3 ~/.automaton/scripts/status.py --create-task add-user-auth --project /path/to/project
 
 # Check task status
-python ~/.automaton/scripts/status.py --task add-user-auth --project /path/to/project
+python3 ~/.automaton/scripts/status.py --task add-user-auth --project /path/to/project
 
 # List all tasks
-python ~/.automaton/scripts/status.py --list --project /path/to/project
+python3 ~/.automaton/scripts/status.py --list --project /path/to/project
 
 # Transition to next phase
-python ~/.automaton/scripts/status.py --transition research --task add-user-auth --project /path/to/project
-python ~/.automaton/scripts/status.py --transition research:awaiting_approval --task add-user-auth --project /path/to/project
+python3 ~/.automaton/scripts/status.py --transition research --task add-user-auth --project /path/to/project
+python3 ~/.automaton/scripts/status.py --transition research:awaiting_approval --task add-user-auth --project /path/to/project
 
 # Approve a phase (after user sign-off)
-python ~/.automaton/scripts/status.py --approve --task add-user-auth --project /path/to/project
+python3 ~/.automaton/scripts/status.py --approve --task add-user-auth --project /path/to/project
 
 # Validate task folder
-python ~/.automaton/scripts/status.py --validate-folder --task add-user-auth --project /path/to/project
+python3 ~/.automaton/scripts/status.py --validate-folder --task add-user-auth --project /path/to/project
 
 # Audit all tasks
-python ~/.automaton/scripts/status.py --audit --project /path/to/project
+python3 ~/.automaton/scripts/status.py --audit --project /path/to/project
 
 # Upgrade pre-v2.0 tasks (bootstrap .state files)
-python ~/.automaton/scripts/status.py --upgrade --project /path/to/project
+python3 ~/.automaton/scripts/status.py --upgrade --project /path/to/project
 
 # Check if code edits are allowed (harness integration)
-python ~/.automaton/scripts/status.py --can-edit --project /path/to/project
-python ~/.automaton/scripts/status.py --can-edit --project /path/to/project --file src/main.py
-python ~/.automaton/scripts/status.py --can-edit --project /path/to/project --task add-user-auth --json
+python3 ~/.automaton/scripts/status.py --can-edit --project /path/to/project
+python3 ~/.automaton/scripts/status.py --can-edit --project /path/to/project --file src/main.py
+python3 ~/.automaton/scripts/status.py --can-edit --project /path/to/project --task add-user-auth --json
 ```
 
 **Important**: Always pass `--project` to ensure correct scoping when multiple projects exist. Without it, `status.py` resolves the project from the current directory and errors if not in a project.
@@ -239,10 +239,10 @@ Tasks without `.state` files are UNTRACKED — all commands (`--transition`, `--
 To fix untracked tasks:
 ```bash
 # Upgrade a single task
-python ~/.automaton/scripts/status.py --upgrade --task my-old-task --project /path/to/project
+python3 ~/.automaton/scripts/status.py --upgrade --task my-old-task --project /path/to/project
 
 # Upgrade all tasks at once
-python ~/.automaton/scripts/status.py --upgrade --project /path/to/project
+python3 ~/.automaton/scripts/status.py --upgrade --project /path/to/project
 ```
 
 ### Enforcement
@@ -321,7 +321,7 @@ This will:
 
 You can also upgrade tasks individually:
 ```bash
-python ~/.automaton/scripts/status.py --upgrade --task my-task --project /path/to/project
+python3 ~/.automaton/scripts/status.py --upgrade --task my-task --project /path/to/project
 ```
 
 #### Installing the pre-commit hook manually
@@ -335,7 +335,7 @@ ln -sf ~/.automaton/scripts/git-hooks/pre-commit .git/hooks/pre-commit
 
 To verify the hook is working:
 ```bash
-python ~/.automaton/scripts/status.py --can-edit --project /path/to/project
+python3 ~/.automaton/scripts/status.py --can-edit --project /path/to/project
 # Should return exit code 1 (DENIED) if no tasks are in implement/doc_review
 ```
 
@@ -350,7 +350,7 @@ The dashboard provides a web-based Kanban board, statistics, and timeline views
 
 ```bash
 # Start from any project root or ~/.automaton/
-python -m automaton.dashboard
+python3 -m automaton.dashboard
 
 # Or use the convenience wrapper
 bash ~/.automaton/scripts/dashboard.sh