refactor(skills): migrate pr-risk-assessment from CLAUDE_CONFIG_DIR to FULLSEND_SKILLS_DIR

Replace runtime-specific CLAUDE_CONFIG_DIR path references with the
runtime-neutral FULLSEND_SKILLS_DIR env var so pr-risk-assessment
scripts work on any supported runtime, not just Claude.

- Update script invocation path in SKILL.md and risk-assessment.md
- Update header comment in risk-tier1.sh
- Add FULLSEND_SKILLS_DIR to SANDBOX_RUNTIME_VARS in reachability test
- Remove resolved KNOWN_GAPS entry for pr-risk-assessment:CLAUDE_CONFIG_DIR

AI-Assisted: true
Assisted-by: claude-opus-4-6
Generated with AI assistance (claude-opus-4-6)

Signed-off-by: Jay Flowers <jay.flowers@gmail.com>

Author: jflowers

scripts/skill-env-reachability-test.sh

@@ -40,6 +40,7 @@ SANDBOX_RUNTIME_VARS=(
   FULLSEND_OUTPUT_DIR
   FULLSEND_OUTPUT_SCHEMA
   FULLSEND_ROLE
+  FULLSEND_SKILLS_DIR
   GOOGLE_APPLICATION_CREDENTIALS
   PATH
 )
@@ -131,10 +132,6 @@ declare -A KNOWN_GAPS=(
   ["github-forge:ISSUE_NUMBER"]="#1664 — forge skill derives ISSUE_NUMBER locally from ISSUE_URL; not in fix/retro/review/prioritize/triage env.sandbox"
   ["gitlab-forge:ISSUE_NUMBER"]="#1664 — forge skill derives ISSUE_NUMBER locally from ISSUE_URL; not in fix/retro/review/prioritize/triage env.sandbox"
   ["issue-labels/gitlab:ISSUE_NUMBER"]="#1664 — label skill derives ISSUE_NUMBER locally from ISSUE_URL; review/triage harnesses do not supply it"
-  # pr-risk-assessment scripts hard-reference the runtime-specific config
-  # dir (CLAUDE_CONFIG_DIR on claude; CODEX_HOME/PI_CODING_AGENT_DIR on
-  # codex/pi). No runtime-neutral skill path exists yet.
-  ["pr-risk-assessment:CLAUDE_CONFIG_DIR"]="#1672 — runtime-specific config dir; needs runtime-neutral skill path"
   # Skills below reference these vars as ${VAR} expansions without
   # assigning them, and no delivering harness declares them in
   # env.sandbox.

skills/pr-review/sub-agents/risk-assessment.md

@@ -24,7 +24,7 @@ review verdicts.
 
 1. Run the Tier 1 metadata script:
    ```bash
-   bash "${CLAUDE_CONFIG_DIR}/skills/pr-risk-assessment/scripts/risk-tier1.sh"
+   bash "${FULLSEND_SKILLS_DIR}/pr-risk-assessment/scripts/risk-tier1.sh"
    ```
    Capture the KEY=VALUE output. Each line is one signal.
 

skills/pr-risk-assessment/SKILL.md

@@ -204,7 +204,7 @@ response directly.
 
 1. **Run Tier 1 script:**
    ```bash
-   bash "${CLAUDE_CONFIG_DIR}/skills/pr-risk-assessment/scripts/risk-tier1.sh"
+   bash "${FULLSEND_SKILLS_DIR}/pr-risk-assessment/scripts/risk-tier1.sh"
    ```
    Capture KEY=VALUE output. Parse each line and store signals.
 

skills/pr-risk-assessment/scripts/risk-tier1.sh

@@ -2,7 +2,7 @@
 # risk-tier1.sh — Compute deterministic Tier 1 metadata signals for PR risk assessment.
 #
 # Run by the risk-assessment sub-agent inside the sandbox:
-#   bash "${CLAUDE_CONFIG_DIR}/skills/pr-risk-assessment/scripts/risk-tier1.sh"
+#   bash "${FULLSEND_SKILLS_DIR}/pr-risk-assessment/scripts/risk-tier1.sh"
 #
 # Required env vars: PR_NUMBER, REPO_FULL_NAME, GH_TOKEN
 # Output: KEY=VALUE pairs on stdout, one per line.