chore: align CI Python matrix with devguide lifecycle + fix bash 3.2 portability

[mnriem]

Summary

Aligns Spec Kit's CI Python matrix with the Python release lifecycle, and fixes the bash 3.2 (macOS) portability issues this surfaced.

Policy:

• Floor stays at requires-python = ">=3.11" — the oldest non-EOL security release. Security-only versions (3.11, 3.12) are supported by claim and fixed reactively, not gated on a wide per-commit matrix. (No change to pyproject.toml — upstream already requires 3.11.)
• Test matrix runs only the bugfix (maintenance) releases — 3.13 and 3.14 — which are the versions most likely to surface real differences.
• ruff lint job points at the latest interpreter (3.14) so packaging/lint is exercised on the newest release.
• Added macos-latest to the OS matrix (now ubuntu/windows/macos × 3.13/3.14) so macOS regressions are caught.

bash 3.2 portability fixes

Adding macos-latest surfaced two pre-existing incompatibilities with bash 3.2, which macOS still ships as the system /bin/bash:

1. update-agent-context.sh embeds Python heredocs inside $(...) command substitution. bash 3.2 mis-parses an apostrophe in a heredoc body nested in $(...), failing with an unexpected EOF quote-matching error. Removed the apostrophes from the affected $()-nested heredoc body and documented the constraint inline to prevent regressions.
2. create-new-feature-branch.sh and create-new-feature.sh used the bash 4+ ${word^^} uppercase expansion, which errors as a bad substitution on bash 3.2 and caused short uppercase acronyms (e.g. GO) to be dropped from derived branch names. Replaced with a portable tr '[:lower:]' '[:upper:]' pipeline.

Validation

• Full test suite passes under bash 3.2.57 (verified locally on macOS by forcing bash → /bin/bash).
• shellcheck --severity=error clean on all changed scripts.
• All .sh files parse under bash 3.2 (bash -n).

Notes

• 3.13 enters security-only status in Oct 2026, at which point the matrix rolls to 3.14/3.15.

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This PR was prepared by GitHub Copilot (model: Claude Opus 4.8) on behalf of @mnriem.

[Copilot]

Pull request overview

Aligns Spec Kit’s declared Python support policy and documentation with the Python release lifecycle by lowering the minimum supported version to 3.10 and tightening CI coverage to current bugfix (maintenance) releases.

Changes:

• Lowered requires-python to >=3.10 (pyproject + PEP 723 script header).
• Updated CI test matrix to run on Python 3.13/3.14 across ubuntu/windows/macos.
• Updated user and contributor docs to state “Python 3.10+”.

Show a summary per file

File	Description
src/specify_cli/__init__.py	Updates the embedded PEP 723 requires-python header to 3.10+.
pyproject.toml	Lowers package requires-python floor to >=3.10.
.github/workflows/test.yml	Moves pytest matrix to Python 3.13/3.14 and adds macOS to the OS matrix.
README.md	Updates prerequisites to “Python 3.10+”.
docs/installation.md	Updates install prerequisites to “Python 3.10+”.
docs/install/air-gapped.md	Updates offline install note to “Python 3.10+”.
CONTRIBUTING.md	Updates contributor prerequisites to “Python 3.10+”.

Review details

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• Files reviewed: 7/7 changed files
• Comments generated: 1
• Review effort level: Low

[Copilot]

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 2
• Review effort level: Low

[mnriem]

Addressed both review comments in b247298:

• create-new-feature.sh (non-portable \b): replaced the \b...\b grep word-boundary with grep -qw (BSD grep treats \b as a backspace, so the acronym-preservation branch could silently miss). It now matches its twin create-new-feature-branch.sh, and the description is piped via printf '%s' instead of echo. I also switched the twin's acronym check to printf '%s' so both scripts are byte-for-byte identical in that branch.
• update-agent-context.sh (awkward comment): reworded the self-seeding comment to be clearer while staying apostrophe-free (the bash 3.2 $()-nested-heredoc constraint).

Verified under bash 3.2.57 (full bash-script suite green) and shellcheck --severity=error.

Posted on behalf of @mnriem by GitHub Copilot (model: Claude Opus 4.8).

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Review details

• Files reviewed: 4/4 changed files
• Comments generated: 0 new
• Review effort level: Low