fix: PR File Ingestion Fails for Valid Git Paths Longer Than 500 Characters

[jonathanchang31]

Summary

This PR fixes PR file ingestion failures for valid Git paths longer than 500 characters.
The mirror previously stored PR file paths in VARCHAR(500) columns. Valid Git/GitHub file paths can exceed that length, causing Postgres to reject PR_FILES ingestion with:

ERROR: value too long for type character varying(500)

This change stores PR file paths as TEXT so long valid paths can be ingested, stored, and returned through the mirror API.

Related Issue

Fixes #134

Change Type

• Bug fix
• Database schema change
• Runtime ingestion fix
• API behavior fix
• Scoring data reliability fix
• New feature
• Refactor only
• Documentation only

Real Behavior Proof

Before the fix, a valid 602-character Git path failed at the DB layer:

ERROR: value too long for type character varying(500)

After the fix, the same long path inserts and reads back correctly:

filename_length=602 previous_filename_length=606
602  606  602  new

API readback also succeeds:

{
  "repo_full_name": "codex-smoke/api-long-path",
  "pr_number": 7,
  "scoring_data_stored": true,
  "file_count": 1,
  "filename_length": 602,
  "head_content": "export const x = 1;"
}

Checklist

• Fixes the reported issue
• Keeps the change scoped to PR file path storage
• Includes DB patch for existing deployments
• Updates fresh schema files
• Updates TypeORM entities
• Validates real long-path behavior
• Validates DAS still builds and runs
• Validates connected gittensor tests still pass
• Does not change scoring logic
• Does not introduce unrelated behavior changes