Support Python 3.14 template strings in formatter

[alexmojaki]

Summary

• run the lint job with Python 3.14 so pyright can resolve string.templatelib
• add guarded runtime support for Python 3.14 template strings in the formatter
• cover template string formatting and conversion errors

Tests

• uv run --python 3.14 pyright
• uv run --python 3.14 pytest tests/test_formatter.py -q
• uv run --python 3.14 pre-commit run --files .github/workflows/main.yml logfire/_internal/formatter.py tests/test_formatter.py

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View logs

[cubic-dev-ai]

No issues found across 3 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

[devin-ai-integration]

Devin Review found 0 potential issues.

View 2 additional findings in Devin Review.

[Viicos]

You should then be able to drop the assert isinstance(format_string, str) call below:

Suggested change

	def is_template_string(format_string: object) -> TypeGuard[Template]:
	def is_template_string(format_string: object) -> TypeIs[Template]:

[alexmojaki]

this is ai slop, ignore for now