chore: SessionStart hook to install polyglot toolchains

Ephemeral web containers lose installed tools on restart. Add an idempotent,
non-fatal SessionStart hook that (re)installs GNAT+gprbuild+GnuCOBOL (apt),
ponyc (ponyup), and Alire alr 2.1.1 when missing, and ensures ponyc is on PATH.
Appended alongside the existing R/Octave session-start hook. User-authorized.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015hmgREHNsxYCuim33yUF2c

.claude/settings.json

@@ -6,6 +6,10 @@
           {
             "type": "command",
             "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/session-start.sh"
+          },
+          {
+            "type": "command",
+            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/install-toolchains.sh"
           }
         ]
       }