Detect variants for stand-alone port frozen stubs instead of collapsing to GENERIC

[Copilot]

For stand-alone ports (webassembly, unix, windows), every variant manifest was being written to a single <port>/GENERIC/ folder, overwriting earlier variants and not matching the path that combo_sources() / default_board() expect (e.g. webassembly/PYSCRIPT, unix/STANDARD). Reproducer: stubber build --port webassembly --version v1.26.1.

Root cause

get_portboard() only matched ports/<port>/boards/<board>/. Stand-alone ports use ports/<port>/variants/<variant>/manifest.py (or a port-level manifest.py for the implicit standard variant), so board came back empty for every variant and get_freeze_path() defaulted them all to legacy GENERIC.

Changes

• publish/defaults.py — add STAND_ALONE_PORTS = {"unix", "windows", "webassembly"} and STANDARD_VARIANT = "standard".
• freeze/common.py
  • get_portboard() regex now also captures variants/<variant>; returns (port, board, variant).
  • get_freeze_path(stub_path, port, board, variant="") uses variant (or "standard" for stand-alone ports) when no board is given. Non-stand-alone ports keep the GENERIC fallback for backward compatibility.
• freeze/freeze_manifest_2.py
  • make_path_vars() resolves BOARD_DIR to ports/<port>/variants/<variant> when a variant is provided so manifests execute in the correct working directory.
  • freeze_one_manifest_2() / copy_frozen_to_stubs() thread variant through.
• freeze/freeze_folder.py — consume the new 3-tuple.
• Tests — update test_get_portboard for the 3-tuple, add variant-path cases, add test_get_freeze_path covering board / variant / stand-alone-default-to-STANDARD resolution.
• .gitignore — exclude repos/ to keep generated DBs out of the tree.

Resulting freeze folders

Manifest path	Before	After
ports/webassembly/manifest.py	webassembly/GENERIC	webassembly/STANDARD
ports/webassembly/variants/pyscript/manifest.py	webassembly/GENERIC (collision)	webassembly/PYSCRIPT
ports/unix/variants/standard/manifest.py	unix/GENERIC	unix/STANDARD
ports/unix/variants/minimal/manifest.py	unix/GENERIC (collision)	unix/MINIMAL
ports/esp32/boards/manifest.py	esp32/GENERIC	esp32/GENERIC (unchanged)
ports/stm32/boards/PYBV11/...	stm32/PYBV11	stm32/PYBV11 (unchanged)

Notes / follow-ups

• get_portboard() is now a 3-tuple; only in-tree callers and one test consume it, all updated.
• The CLI default of GENERIC for --board still resolves correctly for stand-alone ports via default_board() (which already returns pyscript/standard), so no CLI default change was needed in this PR — flagged in the issue as a separate follow-up to revisit alongside per-port build defaults.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.10%. Comparing base (ad9e411) to head (e1e7375).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #740      +/-   ##
==========================================
+ Coverage   72.06%   72.10%   +0.03%     
==========================================
  Files          71       71              
  Lines        8399     8410      +11     
  Branches     1541     1544       +3     
==========================================
+ Hits         6053     6064      +11     
  Misses       1837     1837              
  Partials      509      509              

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