Machine-settings layer + canonical user data dir

[kfox]

Summary

Adds a machine-local settings overlay applied to every run type, and moves persisted machine-specific data (DAC calibrations, WLED + loop presets) to a canonical user data dir — so c64cast works identically from a repo checkout, a pip install, or a future PyPI wheel. This retires the four Path(__file__).resolve().parent.parent repo-anchored globals, which were a latent bug for any non-editable install.

New c64cast/paths.py (stdlib-only, no intra-package imports)

Single source of truth for locations, resolved at use time so env overrides + tests work:

• settings_path() → ~/.config/c64cast/settings.toml (XDG-aware; %APPDATA%\c64cast\ on Windows; $C64CAST_SETTINGS overrides)
• data_root()/calibration_dir()/presets_dir()/loop_presets_dir() → ~/.local/share/c64cast (XDG; %LOCALAPPDATA%; $C64CAST_DATA_DIR overrides)
• legacy_data_root() → the old repo anchor, only for doctor's mv hints

Machine settings (config.py)

load_machine_settings/apply_machine_settings overlay the file as the lowest layer above dataclass defaults, hooked into load, load_master (the ensemble master-defaults Config gets the overlay first, and apply_master_defaults takes a machine-overlaid baseline so master TOML still beats machine settings), and quickcast.build_config. Precedence:

defaults → machine settings → project/per-system TOML → master cascade → CLI → env

[[scenes]]/[ensemble] in the file are rejected (it holds cross-run defaults, not playlists). The per-section apply loop is factored into _apply_toml_sections so the machine file and project file share identical code (unknown-key warnings, validations, the [color] special case).

--save-settings (cli.py)

A config-free command that persists this invocation's machine-relevant flags — -u/--url (decomposed via connect.parse_connection_uri), -d/--device, --sid-model, -s/--system — into the settings file: merges with any existing file, writes it sparsely + atomically, prints it, exits 0. Nothing savable → exit 2. $C64CAST_URL never auto-saves; the DMA password can never be written.

Data-dir consolidation

dac_calibration, transport, and wled_device now resolve their paths through paths.*; save_calibration uses the shared atomic writer.

Doctor

_probe_machine_settings + _probe_data_dirs in the ENVIRONMENT section report the resolved settings + data locations and — from a source checkout with old files still at the legacy calibration//presets/ dirs — the exact mv to migrate them. No implicit migration.

Tests

New test_paths + test_save_settings; machine-settings precedence coverage across config/ensemble/quickcast; the previously-missing C64CAST_DMA_PASSWORD env-precedence test; dir-redirect tests switched from the removed module globals to $C64CAST_DATA_DIR. A shared MachineSettingsIsolation helper keeps the load/round-trip suites hermetic against a real settings file on the developer's machine.

No config-schema change (make schema is a no-op).

Verification

• Full gates green: ruff, mypy --strict (config.py included), pyright, 2601 tests, schema-drift.
• No-hardware end-to-end: --save-settings writes a sparse/annotated/secret-free file and merges; --doctor ENVIRONMENT shows settings + data dir + legacy mv hints; quick playback inherits the settings connection with no -u.
• Real hardware smoke: settings-driven playback rendered correctly on a real U64 with no -u (connection sourced from the settings file).

[codecov]

Codecov Report

❌ Patch coverage is 91.42857% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.56%. Comparing base (1070ea8) to head (b326307).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
c64cast/cli.py	81.81%	5 Missing and 1 partial ⚠️
c64cast/paths.py	84.61%	4 Missing and 2 partials ⚠️
c64cast/config.py	94.44%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #135      +/-   ##
==========================================
+ Coverage   80.37%   80.56%   +0.19%     
==========================================
  Files          86       87       +1     
  Lines       19700    19843     +143     
  Branches     2947     2969      +22     
==========================================
+ Hits        15834    15987     +153     
+ Misses       3187     3163      -24     
- Partials      679      693      +14     

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