refactor: rewrite parse-deps.py as pure bash, remove only Python from repo

Replace lib/parse-deps.py with lib/parse-deps.sh to keep the toolchain
all-bash. Rewrite supervisor P3b cycle detection and P3c stale dep check
as pure bash using associative arrays and DFS.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/parse-deps.py

@@ -1,59 +0,0 @@
-#!/usr/bin/env python3
-"""Extract dependency issue numbers from an issue body.
-
-Usage:
-    echo "$ISSUE_BODY" | python3 lib/parse-deps.py
-    python3 lib/parse-deps.py "$ISSUE_BODY"
-    python3 lib/parse-deps.py --json < issues.json
-
-Modes:
-    stdin/arg:  reads a single issue body, prints one dep number per line
-    --json:     reads a JSON array of issues from stdin, prints JSON
-                dep graph: {"issue_num": [dep1, dep2], ...}
-
-Matches the same logic as dev-poll.sh get_deps():
-  - Sections: ## Dependencies / ## Depends on / ## Blocked by
-  - Inline: "depends on #NNN" / "blocked by #NNN" anywhere
-  - Ignores: ## Related (safe for sibling cross-references)
-"""
-import json
-import re
-import sys
-
-
-def parse_deps(body):
-    """Return sorted list of unique dependency issue numbers from an issue body."""
-    deps = set()
-    in_section = False
-    for line in (body or "").split("\n"):
-        if re.match(r"^##?\s*(Depends on|Blocked by|Dependencies)", line, re.IGNORECASE):
-            in_section = True
-            continue
-        if in_section and re.match(r"^##?\s", line):
-            in_section = False
-        if in_section:
-            deps.update(int(m) for m in re.findall(r"#(\d+)", line))
-        if re.search(r"(depends on|blocked by)", line, re.IGNORECASE):
-            deps.update(int(m) for m in re.findall(r"#(\d+)", line))
-    return sorted(deps)
-
-
-if __name__ == "__main__":
-    if len(sys.argv) > 1 and sys.argv[1] == "--json":
-        issues = json.load(sys.stdin)
-        graph = {}
-        for issue in issues:
-            num = issue["number"]
-            deps = parse_deps(issue.get("body", ""))
-            deps = [d for d in deps if d != num]
-            if deps:
-                graph[num] = deps
-        json.dump(graph, sys.stdout)
-        print()
-    else:
-        if len(sys.argv) > 1:
-            body = sys.argv[1]
-        else:
-            body = sys.stdin.read()
-        for dep in parse_deps(body):
-            print(dep)

lib/parse-deps.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+# parse-deps.sh — Extract dependency issue numbers from an issue body
+#
+# Usage:
+#   echo "$ISSUE_BODY" | bash lib/parse-deps.sh
+#
+# Output: one dep number per line, sorted and deduplicated
+#
+# Matches:
+#   - Sections: ## Dependencies / ## Depends on / ## Blocked by
+#   - Inline: "depends on #NNN" / "blocked by #NNN" anywhere
+#   - Ignores: ## Related (safe for sibling cross-references)
+
+BODY=$(cat)
+
+{
+  # Extract #NNN from dependency sections
+  echo "$BODY" | awk '
+    BEGIN { IGNORECASE=1 }
+    /^##? *(Depends on|Blocked by|Dependencies)/ { capture=1; next }
+    capture && /^##? / { capture=0 }
+    capture { print }
+  ' | grep -oP '#\K[0-9]+' || true
+
+  # Also check inline deps on same line as keyword
+  echo "$BODY" | grep -iE '(depends on|blocked by)' | grep -oP '#\K[0-9]+' || true
+} | sort -un