fix(pg-many-to-many): auto-disambiguate type name collisions instead of crashing

[pyramation]

Summary

Fixes the pg-many-to-many plugin crash when two different FK paths from table A to table B produce the same GraphQL edge type name (e.g. AppBucketAppFilesManyToManyEdge).

Root cause: The custom _manyToManyRelation inflector in custom-inflector.ts had a counting bug — it skipped junction tables where the junction IS the right table (rel.remoteResource?.codec?.name !== rightTable.codec.name). When files acts as both junction and right table (self-referential FK), it wasn't counted, so both paths got the simplified name → same type name → crash.

Two fixes applied:

1. Inflector counting fix (custom-inflector.ts): Removed the !== rightTable.codec.name condition so self-junction paths are properly counted. When multiple m2m paths to the same right table exist, the inflector falls back to the verbose (unique) naming.

2. Defense-in-depth (many-to-many-preset.ts): Added a build hook that wraps registerObjectType to catch type naming conflicts specifically for many-to-many types and silently skip the duplicate. This prevents crashes even in unforeseen edge cases.

Why opt-in didn't prevent this: The ManyToManyOptInPlugin gates field creation via pgManyToMany behavior, but the upstream plugin's init hook calls createManyToManyConnectionType (which registers types) for all discovered relationships unconditionally — before behavior filtering. So even with -manyToMany default, types still get registered and can collide.

Closes constructive-io/constructive-planning#797

Review & Testing Checklist for Human

• Verify the inflector change doesn't break existing m2m type names in your schema (run your app's GraphQL introspection and compare type names before/after)
• Confirm the defense-in-depth registerObjectType wrapper doesn't silently swallow legitimate type conflicts in non-m2m scenarios (it only catches errors whose origin string contains "many-to-many")

Notes

• The integration test adds buckets, files (with self-referential parent_id FK), and file_events tables to the existing preset-integration.test.ts to reproduce the exact collision scenario from the issue
• Tests verify: schema builds without crash, m2m edge types are unique (no duplicates), and m2m types exist in the schema when opted-in via @behavior +manyToMany
• All 51 CI checks pass

Link to Devin session: https://app.devin.ai/sessions/1db04105a50342578181794804059512
Requested by: @pyramation

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring