fix(airt): never overwrite hand-patched workflow files on regen (ENG-6813)

[rdheekonda]

Fixes ENG-6813.

Summary

Workflow generation wrote each script to WORKFLOWS_DIR/<filename> with an unconditional filepath.write_text(script), clobbering any existing file at that path — including one a user had hand-patched after generation. Timestamped filenames (%Y%m%d_%H%M%S) only reduced collisions implicitly; a same-second regen (or any explicit/non-timestamped name) still silently overwrote prior work.

Fix

Add _unique_workflow_path(filename): if the target already exists, save as a new versioned file (name_v2.py, name_v3.py, …) and return the actual filename so callers (summary + execute_workflow next-step hint) report the real file. Existing files are never touched.

Applied at all five generate_* save sites (single, category sweep, agentic, image, tabular). Also removed a duplicate METADATA_FILE assignment.

Bumps capability 1.4.0 → 1.4.1.

Tests

TestUniqueWorkflowPath (3 cases):

• no collision → original name
• collision → saves _v2, leaves the hand-patched original byte-for-byte intact
• repeated collisions → increments to first free _vN

Test plan

• python -m pytest tests/test_attack_runner.py — 103 passed (incl. 3 new)
• python -c "import ast; ast.parse(...)" — generated module compiles