# Country-code normalization patch

## Problem found in `response 202606171240 session D c home.json`

The response mixed three country identifier systems:

- tachograph numeric nation codes, for example `1`, `12`, `13`;
- tachograph alphabetic nation codes, for example `A`, `CZ`, `D`;
- ISO 3166-1 alpha-2 codes returned by Nominatim, for example `AT`, `CZ`, `DE`.

The projection contained 94 numeric `country` values, 33 numeric `countryFrom`
values, and 33 numeric `countryTo` values. The flat and nested trip segments also
contained numeric country identifiers.

This was not only a presentation problem. A tachograph value such as `13` and a
Nominatim value such as `DE` were considered different. The supplied response
contained 15 false reverse-geocoded country changes of the form `13 -> DE` or
`12 -> CZ`, creating unnecessary country segments.

## Canonical representation

All runtime country fields are now exposed and compared as ISO 3166-1 alpha-2.
Examples:

| Tachograph numeric | Tachograph alphabetic | Canonical ISO alpha-2 |
|---:|---|---|
| `1` | `A` | `AT` |
| `12` | `CZ` | `CZ` |
| `13` | `D` | `DE` |

Numeric and alphabetic tachograph values are resolved through the existing
`TachographNationRegistry` and then converted to ISO alpha-2. Nominatim results
are validated and normalized as ISO values.

## Processing changes

Normalization is applied before country comparison and at the main presentation
boundaries:

- normalized EventHub support evidence;
- source-neutral runtime support events;
- tachograph file-session support-event adapters;
- legacy tachograph Esper result conversion;
- `projection.supportGeoEvents`;
- flat country-trip segments;
- country segments nested under HOME-to-HOME trips;
- Nominatim country-code parsing.

The original source payload remains available in raw event attributes where the
numeric tachograph values are needed for diagnostics.

## Expected result

An explicit border crossing `1 -> 13` is represented as `AT -> DE`. A subsequent
Nominatim result `DE` no longer creates a false `13 -> DE` transition. The trip
continues in the same canonical `DE` country state until a genuine country change.