feat(tools): add Python linter script with pytest wrapper

[Copilot]

Summary

Adds tools/lint.py, a single-file Python linter for the Android project that runs as a final validation step before merging.

Checks performed

Check	Description
XML validity	All app/src/main/res/**/*.xml files parse without error
Language parity	Every values-XX/strings.xml contains the same keys as the base values/strings.xml
Language arrays	language_codes and language_names in arrays.xml have the same item count; non-default codes appear in locale_config.xml
Bracket balance	(), {}, [] are balanced in Kotlin/Java source files (strips strings and comments before counting)

Usage

# standalone (exit code = number of failed checks)
python tools/lint.py

# allow up to 3 failures without breaking CI
python tools/lint.py --max-warns 3

# strict mode — extra translation keys are also errors
python tools/lint.py --pedantic

# skip pytest even if installed
python tools/lint.py --no-pytest

When pytest is installed and no special flags are passed, the script delegates to pytest (standard exit codes). Otherwise the built-in standalone runner is used (exit code = failed check count, capped at 125).

Changes

• tools/lint.py — new linter script (argparse, no click; pytest-compatible test_* functions + standalone runner)
• AGENTS.md — new Linting section added after Development best practices, with instructions to run as final step
• .github/workflows/build.yml — Run linter step added before the build
• .github/workflows/release.yml — Run linter step added before the build
• fastlane/metadata/android/en-US/changelogs/1.txt — updated