Add 15 new MCP tools to sx-tree: project-wide search, smart editing, dev workflow

New comprehension tools:
- sx_find_across: search pattern across all .sx files in a directory
- sx_comp_list: list all definitions (defcomp/defisland/defmacro/defpage/define)
- sx_comp_usage: find all uses of a component across files
- sx_diff: structural diff between two .sx files (ADDED/REMOVED/CHANGED)
- sx_eval: REPL — evaluate SX expressions in the MCP server env

Smart read_tree enhancements:
- Auto-summarise large files (>200 lines)
- focus param: expand only matching subtrees, collapse rest
- max_depth/max_lines/offset for depth limiting and pagination

Smart editing tools:
- sx_rename_symbol: rename all occurrences of a symbol in a file
- sx_replace_by_pattern: find+replace first/all pattern matches
- sx_insert_near: insert before/after a pattern match (top-level)
- sx_rename_across: rename symbol across all .sx files (with dry_run)
- sx_write_file: create .sx files with parse validation

Development tools:
- sx_pretty_print: reformat .sx files with indentation (also used by all edit tools)
- sx_build: build JS bundle or OCaml binary
- sx_test: run test suites with structured pass/fail results
- sx_format_check: lint for empty bindings, missing bodies, duplicate params
- sx_macroexpand: evaluate expressions with a file's macro definitions loaded

Also: updated hook to block Write on .sx files, added custom explore agent.

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

.claude/agents/explore.md

@@ -0,0 +1,27 @@
+---
+name: explore
+description: Explore codebase using sx-tree MCP tools for .sx files
+tools: Read, Grep, Glob, Bash, mcp__sx-tree__sx_summarise, mcp__sx-tree__sx_read_tree, mcp__sx-tree__sx_read_subtree, mcp__sx-tree__sx_find_all, mcp__sx-tree__sx_get_context, mcp__sx-tree__sx_get_siblings, mcp__sx-tree__sx_validate
+hooks:
+  PreToolUse:
+    - matcher: "Read"
+      hooks:
+        - type: command
+          command: "bash .claude/hooks/block-sx-edit.sh"
+---
+
+Fast codebase exploration agent. Use for finding files, searching code, and answering questions about the codebase.
+
+## Critical rule for .sx and .sxc files
+
+NEVER use Read on .sx or .sxc files. The hook will block it. Instead use the sx-tree MCP tools:
+
+- `mcp__sx-tree__sx_summarise` — structural overview at configurable depth
+- `mcp__sx-tree__sx_read_tree` — full annotated tree with path labels
+- `mcp__sx-tree__sx_read_subtree` — expand a specific subtree by path
+- `mcp__sx-tree__sx_find_all` — search for nodes matching a pattern
+- `mcp__sx-tree__sx_get_context` — enclosing chain from root to target
+- `mcp__sx-tree__sx_get_siblings` — siblings of a node with target marked
+- `mcp__sx-tree__sx_validate` — structural integrity checks
+
+For all other file types, use Read, Grep, Glob, and Bash as normal.

.claude/hooks/block-sx-edit.sh

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+#!/bin/bash
+# Block Edit/Read/Write on .sx/.sxc files — force use of sx-tree MCP tools
+FILE=$(jq -r '.tool_input.file_path // .tool_input.file // empty' 2>/dev/null)
+if [ -n "$FILE" ] && echo "$FILE" | grep -qE '\.(sx|sxc)$'; then
+  printf '{"decision":"block","reason":"Use sx-tree MCP tools instead of Edit/Read/Write on .sx/.sxc files. For new files use sx_write_file, for reading use sx_read_tree/sx_summarise, for editing use sx_replace_node/sx_rename_symbol/etc. See CLAUDE.md for the protocol."}'
+  exit 2
+fi