fix(medcat-trainer): open FP, FN, and TP example dialogs

[tomolopolis]

Summary

Clicking a non-zero FP, FN, or TP count on a completed metrics report did not reliably open the example dialog.

The count button looked up the concept with Array.indexOf. The metrics table does not always pass the original row object (it can pass a copy, or its internal { type: 'item', raw } wrapper). That lookup returned -1 and the click threw before the dialog was shown.

Examples from current MedCAT get_stats also use snake_case fields (document_id, source_value). The dialog still expected the older spaced keys (document id, source value), so rows that did open could not show the note or link through to the annotation. Clinical text was interpolated into a Vue template without escaping, so characters such as < or {{ could break that render.

The count colours were also lost. Vuetify sets color: inherit on button and [type=button], and later .btn rules reset --bs-btn-color to the default text colour. Non-zero counts now use the NHS theme variables: true positives var(--success), false negatives var(--warning), and false positives var(--danger). Those variables are set from $theme-colors (green, grey, and red). Zero counts stay disabled.

Changes

• Resolve FP/FN/TP examples from the clicked row, then by concept, instead of object identity.
• Accept both the legacy spaced keys and the current snake_case stats payload when rendering and linking examples.
• Escape clinical text before it is compiled as a template, and fall back to the stored context snippet when the full document is unavailable.
• Mount the example dialog on document.body and open it after the click, so it is not clipped or closed by the same click.
• When metrics are calculated, copy both key styles onto each example and look up the annotating user with either key style.
• Paint non-zero TP, FN, and FP counts from the theme colour variables, including a matching hover background so the number stays readable.

Testing

• npx vitest run src/tests/components/MetricsConceptSummary.spec.ts (5 tests passed). The count test checks that non-zero buttons stay enabled and that the theme variables are used.
• In Chrome, with those variables compiled from $theme-colors, a non-zero TP computed to rgb(0, 150, 57), FN to rgb(118, 134, 146), and FP to rgb(218, 41, 28). A zero count stayed the default text colour.
• Python metrics changes were syntax-checked. The Django suite was not run here because the trainer environment (Django, MedCAT, torch) is not installed.