Limit bulk relationship builds to stored maps

[RANGROO]

Problem

Stobe's bulk relationship build queued every NPC found in event history. On the local playthrough this meant 643 pending NPCs, causing broad proximity-derived relationships, excessive LLM requests, and truncation failures.

Change

• Limit bulk status, list, and processing paths to NPCs with non-empty stored relationship maps, matching HerikaServer's migration scope.
• Normalize and copy structured Stobe relationship JSON directly into extended_data without an LLM request.
• Retain the LLM fallback for legacy prose relationship summaries.
• Leave the manual per-NPC Build from Events action unchanged.

Compatibility

No schema migration is required. Existing built relationships remain skipped unless Force Rebuild is selected.

HerikaServer already uses the limited stored-relationship scope. DialecticServer has no equivalent bulk UI and its internal batch analysis already requires stored relationships, so no sibling port is needed.

Validation

• php -l ext/relationship_system/batch_build.php
• php -l ext/relationship_system/relationship_llm.php
• php -l tests/relationship_system_regression.php
• STOBE_DB_NAME=stobe_test php tests/relationship_system_regression.php
• Read-only local stats check: 15 built, 38 pending after limiting the scope, down from 643 pending.
• git diff --check origin/unstable...HEAD

Deployment

Not deployed.

Limits

No browser or in-game bulk build was performed. The separate per-NPC connector-selection issue and faction full-snapshot cleanup issue are outside this PR.