feat: improve gear entry and weight displays

AGENTS.md

@@ -0,0 +1,86 @@
+# Packrat Repository Guide
+
+This file is the authoritative guidance for coding agents working in this repository.
+
+## Project Overview
+
+Packrat is a Python 3.9+ terminal application for maintaining a backpacking gear inventory and building trip-specific pack lists. The UI uses Textual. User data is stored in a portable JSON library selected during onboarding; it is not normally the repository's `gear_data.json`.
+
+## Commands
+
+Use `uv` for the project environment.
+
+```bash
+# Run the application
+uv run python main.py
+
+# Run the committed unittest suite (including headless Textual tests)
+uv run python -m unittest discover -s tests -v
+
+# Run all pytest-style and unittest-style tests when pytest is available
+uv run pytest
+```
+
+For a disposable library during manual testing, pass an exact file path:
+
+```bash
+uv run python main.py --data /tmp/packrat-test/gear_data.json
+```
+
+Do not use a developer's remembered personal library for automated or destructive testing.
+
+## Architecture and Ownership
+
+- `main.py`: minimal entry point; delegates to `gear_tui.main()`.
+- `gear_core.py`: UI-independent data model, validation, calculations, persistence, backups, comparisons, audits, and Markdown rendering. Keep it free of Textual imports and terminal I/O.
+- `packrat_preferences.py`: cross-platform config/data paths, atomic preference persistence, and startup-path precedence.
+- `gear_tui.py`: Textual screens, widgets, bindings, application state, and CSS (`APP_CSS`). UI handlers should delegate domain logic and persistence to `gear_core.py`.
+- `tests/test_core.py`, `tests/test_preferences.py`, `tests/test_tui.py`: current behavioral and headless workflow coverage.
+- `tests/unit/`: additional unit coverage; preserve compatibility with it when changing core behavior.
+
+Maintain the boundary between the pure core and the UI. If behavior can be expressed without Textual widgets, implement it in `gear_core.py` and test it there.
+
+## Data and Persistence Invariants
+
+- `gear_core.DATA_VERSION` is the current schema version. `validate_data()` accepts supported older data, supplies backward-compatible defaults, rejects ambiguous/invalid values, and upgrades the in-memory version.
+- Gear and trip IDs are non-empty strings and unique within their collection. Generate sequential IDs with `next_id()` (`G001`, `T001`, and so on).
+- All stored weights are ounces. Convert to pounds only for display or export.
+- Inventory quantity and trip-specific quantity are distinct. A trip item contains `gear_id`, `qty`, and `note`; calculations must use the trip quantity.
+- Trip audit values must use `AUDIT_STATUSES`; categories and weight types must use the canonical constants.
+- Validate the complete model before saving. Preserve atomic writes, `.bak` creation, file signatures, conflict detection, and rollback-on-failure behavior.
+- Exports belong in the `exports/` directory beside the active data file, as determined by `export_dir_for_data()`.
+- The `--data` option is a one-launch exact-file override and must not update remembered preferences.
+- The selected persistent storage directory always contains a library named `gear_data.json`.
+
+When adding or changing persisted fields, update all affected layers together:
+
+1. `blank_data()`, `example_data()`, validation/defaulting, and schema version/migration behavior as appropriate.
+2. Calculations, duplication/comparison/audit logic, and Markdown renderers that consume the field.
+3. The relevant Textual form and save/read paths.
+4. Core tests plus headless UI coverage for user-visible workflows.
+
+Never silently coerce malformed persisted values when doing so could change pack weights or meaning.
+
+## UI Conventions
+
+- Keep visual styling centralized in `APP_CSS`.
+- Preserve keyboard and mouse parity. Existing global bindings include `1`/`2`/`3`, `/`, `?`, `Ctrl+B`, `Ctrl+P`, `q`, and `Ctrl+C`.
+- Use `@on(...)` handlers and typed `query_one(selector, WidgetClass)` calls where practical.
+- Strip text input, parse numeric fields explicitly, and notify with `severity="error"` rather than dismissing a form with invalid data.
+- Modal forms use `Ctrl+S` to save and `Esc` to cancel. Confirmations must remain explicit for destructive actions.
+- After a mutation, persist through `GearTrackerApp.save()` and refresh the affected view. Do not bypass its conflict handling or rollback behavior.
+
+## Testing Expectations
+
+- Add or update tests with every behavioral change.
+- Prefer focused core tests for calculations, validation, migration, persistence, and Markdown output.
+- Use Textual Pilot tests for navigation, bindings, dialogs, and complete keyboard workflows; do not rely only on manual UI checks.
+- Use temporary directories and injected preference paths for filesystem tests. Tests must not read or modify real user preferences or libraries.
+- Run at least `uv run python -m unittest discover -s tests -v` before handing off a change. Run `uv run pytest` too when modifying behavior covered by `tests/unit/`.
+- Maintain Python 3.9 compatibility; avoid syntax and standard-library APIs introduced later.
+
+## Dependencies and Style
+
+- Add runtime dependencies to `pyproject.toml` with `uv add`; commit the resulting `uv.lock` change. Keep `requirements.txt` aligned for pip users when runtime dependencies change.
+- Use clear names and small, focused functions. Comment rationale and non-obvious constraints, not mechanics visible from the code.
+- Preserve unrelated working-tree changes. Generated caches, logs, personal data, and exports should not be committed unless the task explicitly requires a fixture or artifact.

README.md

@@ -75,7 +75,10 @@ are:
   item by accident.
 - **Gear Inventory tab** — search, add, edit, delete gear. The "Review
   Candidates" button filters to items rated low usefulness (<3/5) *and*
-  over 8 oz — good first candidates to cut.
+  over 8 oz — good first candidates to cut. Enter each item's per-unit weight
+  in ounces; Packrat immediately previews and displays the equivalent ounces,
+  pounds, and grams throughout the app and its exports. Save and Cancel remain
+  visible while long gear forms scroll on compact terminals.
 - **Trips tab** — click a trip to open its dashboard: live weight summary,
   a colored category-weight bar chart, and the assigned-gear list. Add or
   remove items right there; the same gear item can be on any number of