Update CI workflow to use actions/checkout@v6 and adjust test setup to install the package with development dependencies (pip install -e .[dev]) so pytest and other test tooling are available in the test environment. This ensures tests run against the editable package with the required dev deps.

Small housekeeping and bug fixes: remove stray whitespace in the Codespell workflow file, constrain pydantic to >=2,<3 in pyproject to avoid accidental 3.x installs, replace hardcoded '/dev/null' with os.devnull for cross-platform empty-tree hashing, and include deleted files in changed_files by adding 'D' to the git diff-filter so deletions are detected.

Introduce selection provenance and richer human-readable output for the test selector. Changes include: import defaultdict; convert FULL_SUITE_TRIGGERS to labeled (name, predicate) entries (add DEEPLABCUT.yaml trigger); detect and record matching full-suite triggers with a compact count reason; track which categories contributed pytest paths and functional scripts; ensure the minimal pytest fallback is attributed; add explain_changed_files, _render_file_line, and _compute_selection_provenance helper functions; extend _render_decision_markdown to show per-file trigger/category annotations, grouped category views, uncategorized files, and provenance for selected tests/scripts; and move the diff_mode reason to the front of the reasons list for prominence. Also minor deterministic ordering and small refactors to accumulate sources.

Update the GitHub Actions workflow (.github/workflows/python-package.yml) to change the dev dependency install command in the pytest step from `pip install --no-cache-dir -e .[dev]` to `pip install --no-cache-dir -e --group dev`. This switches the workflow to use pip's group-based dev dependency installation while keeping editable installs and no-cache. Note: this may require a newer pip version in the CI image that supports the --group option.

Don't mark files as uncategorized when they matched any full-suite triggers; only append to uncategorized if no categories and no full triggers. Change the per-file icon so full-triggered files use a warning/empty icon instead of a red dot, and leave normal files without an icon. Also comment out adding the diff_mode reason to the top of the reasons list (disables insertion of diff_mode). These tweaks avoid mislabeling files and adjust the UI/metadata emitted by the test selector.

Introduce LINT_ONLY_FILES and treat listed files as lint-only (e.g. .pre-commit-config.yaml) so they are not considered for test selection. explain_changed_files now records a per-file "lint_only" flag, accumulates a lint_only list in the result, and includes that list in the output. The renderer was updated to add a lint-only tag next to affected files and a dedicated markdown section explaining these files don't influence test selection.

Specify the current directory for editable install in the GitHub Actions job. The pip command was changed from `pip install --no-cache-dir -e --group dev` to `pip install --no-cache-dir -e . --group dev` so the editable install has a target path and the workflow won't fail due to a missing package path.

Update test selector markdown rendering to iterate over res.reasons and render each as a code-formatted bullet, skipping entries that start with "diff_mode:" so the diff mode isn't duplicated in the reasons list. Also re-enable inserting the diff_mode into res.reasons (uncommented) so the diff mode remains available for the dedicated Diff mode line.

Introduce concurrency to GitHub Actions to avoid duplicate/in-flight runs. intelligent-testing.yml: add top-level concurrency keyed by PR number or ref and pass a concurrency_key to the called python-package workflow when running a full plan. python-package.yml: add an optional workflow_call input concurrency_key and configure job-level concurrency that uses the provided key (with a run_id fallback) and includes matrix axes (OS and Python version) in the group; cancel-in-progress is enabled. Minor whitespace/formatting adjustments included.

Make concurrency groups deterministic and PR-aware across workflows. intelligent-testing.yml now formats the concurrency group as `pr-{number}` for PRs or `run-{run_id}` for non-PR runs, and passes an empty concurrency_key when not on a PR. python-package.yml adds a comment and refines its concurrency group to use the provided concurrency_key (or fall back to the run ID), so only PR runs with the same OS/Python combination cancel outdated runs while branch/main pushes get unique groups.

Introduce a DiffMode enum and track how diffs were determined (PR, push, manual, fallback, initial). Return DiffMode from determine_diff_range and store it on SelectorResult; expose it to GitHub output. Add MODE_LABELS and CATEGORY_RULE_BY_NAME helper.

Revamp reporting: make _render_decision_markdown configurable (style: minimal|detailed, emoji toggle), compact category reasons, group and paginate changed-file listings, highlight full-suite triggers, and include provenance for selected pytest paths and scripts. Add emoji/no-emoji and report-style CLI flags and pass them into write_report_files. Also write selection.json and decision.md by default and include diff_mode in outputs.

Detect CI-related changes (.github/workflows/ and tools/) as full-suite triggers and add them to FULL_SUITE_TRIGGERS. Temporarily comment out the ci_tools category rule to avoid duplicate handling. Refactor the markdown renderer to produce clearer, collapsible sections: full-suite triggers, files grouped by category (with notes if a category lacks explicit rules), lint-only, and uncategorized files. Make per-file tag/marker rendering configurable, tidy up plan/diff headers, and only include provenance when style is "detailed". Also improve limits/ellipsis handling and minor formatting/emoji adjustments for cleaner output.

Replace the markdown headings for 'Pytest paths' and 'Functional scripts' with HTML <details>/<summary> blocks so those sections are collapsible in the rendered output. Adds corresponding closing </details> tags and newline adjustments. This is a presentation change only—no functional logic was modified.

Add explicit pytest_paths and functional_scripts placeholders to the "docs" category (with comments warning that adding entries will escalate DOCS_ONLY to FAST). Update decide() to detect when the docs category has attached test/script rules and return a FAST plan with those paths (deduplicated and sorted) instead of DOCS_ONLY. Also simplify file tag rendering for lint-only files by emitting only the lint header/icon instead of listing items. These changes ensure docs files with explicit test/script rules run the FAST lane rather than being treated as docs-only.

Add handling for initial pushes and make job summary writing configurable. Changes include:
- Treat a zero SHA (or missing/unknown `before` commit) as an initial commit by using an empty tree and returning DiffMode.INITIAL.
- Change determine_diff_range return type to include DiffMode and add zero_sha sentinel and robustness around missing `before` commits.
- Make append_job_summary accept an overwrite flag (default True) and use write mode when overwriting, otherwise append.
- Minor comment tweak and disable DLC_NAMESPACE constant (commented out).
These changes improve detection of initial push events and let the caller choose whether to overwrite the GitHub Actions job summary file.

Uncomment and enable the ci_tools category rule (matches .github/ and tools/) so it appears in CATEGORY_RULES. Add a new category_only parameter to _render_file_line and adjust tag rendering so full-triggers and lint-only tags are omitted when category_only is true, preventing noisy tags in contexts where only category information is desired.