fix(entries): accept stored asset paths on write (#41)

[sylvesterdamgaard]

Fixes #41.

The bug

statamic-entries get returns an assets field the way Statamic stores it — a container-relative path, icons/heart.svg. Everything downstream of a Control Panel form submission expects the other form: the canonical container::path asset ID, in a list.

So a value round-tripped from get into update fails:

• Statamic\Fieldtypes\Assets\MimesRule::passes() does Asset::find($id), and a bare path finds nothing → "must be a file of type: svg"
• on a field with no file rules it would have got further and then broken in Assets::process(), which calls Asset::findOrFail()

It also hit fields the caller never touched: update validates the incoming data merged with the entry's stored data, and stored data is all paths, so any other assets field carrying required + mimes failed an unrelated update.

The Control Panel bridges this gap in Assets::preProcess() when it loads the form. Anything handing stored values to the validator without that step has to bridge it itself.

Second bug, same root cause

Double-checking the fix turned up content_validate, which sweeps content already on disk and so hands the validator stored values directly. It reported three false errors for every valid single-file assets field:

The Icon field must be a file of type: svg.
The Icon field must be an array.
The Icon field must not have more than 1 items.

The last two come from the fieldtype's own array/max:1 rules, which expect a list rather than the bare string Statamic stores.

The fix

Container and ID resolution live in a new ResolvesAssetIds concern, used from both sides:

• Write path (SanitizesFieldData, so entries, terms and globals alike) — incoming asset paths are resolved before validation, covering nested replicator, bard, grid and group fields as well as top-level ones, and the stored data an update merges in.
• Read path (ValidatesContentRecords) — the rule pass gets a normalized copy of the record. The structural pass keeps the raw values, so a missing_asset finding still quotes the reference exactly as it appears on disk.

Container resolution mirrors the fieldtype's own: the configured container, or the only one that exists. That last part also fixes assetFindings, which previously skipped single-container fields entirely. References that resolve to no asset are passed through untouched, so validation reports the real problem instead of silently dropping content. Canonical IDs continue to work unchanged.

Tests

• tests/Feature/Routers/EntriesAssetRoundTripTest.php — 5 cases covering top-level, replicator, grid and bard-set asset fields on both create and update, an unrelated update that must not trip stored paths, plus regression guards (canonical IDs still accepted, missing asset still rejected).
• ContentValidateTest::test_does_not_report_stored_asset_paths_as_rule_violations — top-level and nested.

Verified against main: 4 of these fail there, all pass here. Full gate green — pint, PHPStan level 9 (no ignores, no baseline), 1106 tests / 5609 assertions, license check.