fix: prevent file corruption in transform download

[bhsf-james-pannell]

he sail transform download command produces corrupted JSON files in two scenarios:

1. Re-downloading to existing folder

WriteFile uses O_CREATE|O_RDWR without O_TRUNC. When new content is shorter than existing file content, leftover bytes remain, producing invalid JSON.

2. Filename collisions

Transform names like "AD - samAccountName" and "AD-samAccountName" both sanitize to AD-samAccountName.json. The second overwrites the first, and combined with bug #1, produces merged/corrupted content.

Changes

• Add O_TRUNC flag to WriteFile to properly truncate existing files
• Add filename collision detection using in-memory map (appends -1, -2, etc.)
• Use sanitize.PathName directly instead of manual space stripping
• Change O_RDWR to O_WRONLY (write-only, since we never read)

Bug: Missing O_TRUNC

Original file (first download):

{
  "name": "ToUpper",
  "type": "upper",
  "attributes": {
    "input": { "type": "identityAttribute" }
  }
}

After transform is updated and re-downloaded (shorter content):

{
  "name": "ToUpper",
  "type": "upper"
}put": { "type": "identityAttribute" }
  }
}

Bug: Filename Collision

First transform written:

{
  "name": "AD - samAccountName",
  "type": "accountAttribute",
  "attributes": {
    "sourceName": "Active Directory"
  }
}

Second transform overwrites (shorter, same sanitized filename):

{
  "name": "AD-samAccountName",
  "type": "static"
}ountAttribute",
  "attributes": {
    "sourceName": "Active Directory"
  }
}

After Fix

transforms/
├── AD-samAccountName.json    # first transform preserved
├── AD-samAccountName-1.json  # collision handled
└── ToUpper.json              # clean on re-download (O_TRUNC)

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[Copilot]

Pull request overview

Fixes corrupted JSON output produced by sail transform download by ensuring files are correctly overwritten and by reducing accidental overwrites from filename collisions.

Changes:

• Truncate existing files on write to prevent leftover trailing bytes from prior content.
• Generate unique filenames for transforms whose names sanitize to the same base filename.
• Use sanitize.PathName for consistent filename sanitization and switch file open mode to write-only.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
internal/output/output.go	Updates file open flags to include truncation (O_TRUNC) when overwriting files.
cmd/transform/download.go	Adds sanitized filename generation plus in-memory collision handling for transform downloads.

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