Add player-only relationship custom info

[RANGROO]

Screenshot

Requested behavior

Add a small Custom Info paragraph field to each relationship. It is empty by default, editable only by the player, and must never be sent to or changed by relationship AI.

Implementation

• Adds Custom Info to the PHP relationship details modal and NPC save handler.
• Persists it as extended_data.relationships[target].custom_info.
• Adds the field to the Prisma NPC Manager save API.
• Excludes the field from relationship prompt construction.
• Strips any model-supplied custom_info value.
• Preserves existing player text during incremental AI changes and full AI rebuilds, including relationships omitted by a rebuild.

No database migration is required. Existing relationship data remains compatible.

Validation

• PHP lint passed for all five changed files.
• RelationshipTypeValidationTest.php: 12 tests, 36 assertions passed.
• Direct relationship AI-isolation probe: 8 assertions passed.
• PHP save/round-trip probe: 3 assertions passed.
• PHP UI checked at desktop and 390px widths with no horizontal overflow.
• Full PHPUnit run reached 268 tests and 2,617 assertions, but ended with 16 errors, 2 failures, and 1 warning from unavailable Windows PostgreSQL/ZipArchive dependencies and cases outside these changed paths.
• git diff --check passed.

Review notes

• Reviewable diff: 124 changed lines across 5 files.
• Overlaps open PR Run relationship worker only for queued evaluations #725 in lib/relationship_manager.php and PR Support distinct profiles for same-named actors #735 in ui/api/chim_npc_manager.php; merge conflict review may be required.
• No production dependency, schema migration, generated artifact, or expected hot-path cost was added.
• Related CHIM Prisma UI draft: Dwemer-Dynamics/CHIM#168.

Deployment and limits

• Locally deployed from 26dcec67d0bd72ba2c4f8f44b380e89914fdb000 to /var/www/html/HerikaServer; all five changed-file SHA-256 hashes match and the server/API return HTTP 200.
• No in-game validation was performed.
• Screenshot attached above.