fix(benchmarks): make agentic fixture path portable via PONYTAIL_TMPL (#206)

tasks.py hardcoded _TMPL to a personal absolute Windows path (D:\dev\...), which the agentic benchmark's Reproduce flow depends on. Resolve it via a PONYTAIL_TMPL env override with a relative fallback, mirroring the existing PONYTAIL_PLUGIN_DIR convention in run.py; run.py's loader resolves the relative name under fixtures/. selftest skips the open tasks that consume _TMPL, so instrument validation is unaffected (verified: all instruments valid).

benchmarks/agentic/README.md

@@ -112,7 +112,8 @@ python complete.py --run runs/<stamp>  # completeness-score every workspace
 ## Reproduce
 
 Needs the `claude` CLI (this is the harness, no SDK), Python 3, an authenticated Claude Code, and a
-clone of the template at the pinned commit (point `_TMPL` in `tasks.py` at it):
+clone of the template at the pinned commit (set `PONYTAIL_TMPL` to its path, or drop it at
+`fixtures/full-stack-fastapi-template`):
 
 ```bash
 git clone https://github.com/fastapi/full-stack-fastapi-template

benchmarks/agentic/tasks.py

@@ -25,7 +25,9 @@ from pathlib import Path
 
 # Real-repo fixture: tiangolo/full-stack-fastapi-template @ cd83fc1 (v0.10.0, MIT), cloned locally.
 # Reproduce: git clone https://github.com/tiangolo/full-stack-fastapi-template && git -C ... checkout cd83fc1
-_TMPL = r"D:\dev\fullstack-fastapi-template"
+# Point PONYTAIL_TMPL at your local clone, or drop it at fixtures/full-stack-fastapi-template
+# (run.py resolves a relative name under fixtures/). Mirrors the PONYTAIL_PLUGIN_DIR override.
+_TMPL = os.environ.get("PONYTAIL_TMPL", "full-stack-fastapi-template")
 
 # --- helpers ---
 _imp_n = 0