fix(scripts): tolerate an unusable integration.json in the Python helper

[jawwad-ali]

Problem

get_invoke_separator() in scripts/python/common.py indexes the parsed JSON directly:

state = json.loads(integration_json.read_text(encoding="utf-8"))
key = state.get("default_integration") or state.get("integration") or ""   # AttributeError
...
except (OSError, json.JSONDecodeError):    # covers neither escape below
    pass

Two shapes escape that tuple, while both of its twins fall back to ".":

1. A non-mapping top level ([], "forge", 42, true, null) is valid JSON, so json.JSONDecodeError never fires and .get() raises AttributeError.
2. A non-UTF-8 file raises UnicodeDecodeError — a ValueError, not an OSError. Realistic on Windows, where PowerShell 5.1's Out-File / > default to UTF-16.

Measured on main — the Python helper crashed on 6 of 7 inputs while bash and PowerShell 5.1 (tested natively) returned "." for every one:

.specify/integration.json	python	bash	pwsh 5.1
{"default_integration":"forge"}	'.'	.	.
[]	AttributeError	.	.
[{"a":1}]	AttributeError	.	.
"forge"	AttributeError	.	.
42	AttributeError	.	.
null	AttributeError	.	.
UTF-16 file	UnicodeDecodeError	.	.

The bash twin keeps its separator="." default when jq → python3 → awk all fail to parse; the PowerShell twin likewise returns ".".

Fix

Split the parse out of the lookup, complete the exception tuple, and guard the top-level shape — matching read_feature_json_feature_directory in this same module, which already does exactly this:

try:
    state = json.loads(integration_json.read_text(encoding="utf-8"))
except (OSError, UnicodeError, json.JSONDecodeError):
    return "."
if not isinstance(state, dict):
    return "."

So this makes get_invoke_separator consistent both with its cross-language twins and with its neighbour in the same file — it was the odd one out.

Verification

• New TestGetInvokeSeparatorTolerance: 6 parametrized non-mapping shapes + the UTF-16 case → 7 fail before, pass after.
• test_hyphen_separator_is_still_honoured — regression guard that the real feature (invoke_separator: "-" for e.g. droid/forge) keeps working; passes before and after.
• tests/test_check_prerequisites_python_parity.py: 19 passed, 8 skipped (the skips are the pre-existing bash/pwsh legs gated off on this machine; baseline was 11 passed, 8 skipped).
• Tests are plain unit tests (no bash/pwsh gating), so they run on every CI platform.
• uvx ruff@0.15.0 check src tests scripts clean.

No behaviour change for a well-formed integration.json: every path that previously returned a value is byte-for-byte identical.

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AI-assisted: authored with Claude Code. I measured all three implementations side by side (PowerShell 5.1 natively on Windows) before writing the fix, and matched the guard style already present in the same module.