feat(file_ops): Implement Branch 4 solution with JSON config and WASI sandbox mapping

Key improvements:
- Eliminated runfiles dependency that was failing with 'no runfiles found'
- Pass all paths (wasmtime, WASM component) via JSON config from Bazel
- Expose WASM component file in file_ops_toolchain
- Map entire Bazel sandbox root to / in WASI sandbox for file access
- Convert operations to absolute paths compatible with WASI sandbox mapping
- Add debug logging for sandbox environment troubleshooting
- Add wasmtime_toolchain_type to go_wasm_component rule

Architecture:
- Bazel passes paths via JSON config to avoid runfiles fragility
- file_ops Go binary locates wasmtime and WASM component from config
- Maps sandbox root to WASI root for hermetic file operations
- Operations are converted to absolute sandbox-root paths

This is a solid Bazel-native foundation that eliminates the runfiles issue.
The remaining work is final path resolution tuning in the WASI sandbox.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: avrabe

MODULE.bazel.lock

@@ -831,6 +831,7 @@ go_wasm_component = rule(
         "@rules_wasm_component//toolchains:tinygo_toolchain_type",
         "@rules_wasm_component//toolchains:wasm_tools_toolchain_type",
         "@rules_wasm_component//toolchains:file_ops_toolchain_type",
+        "@rules_wasm_component//toolchains:wasmtime_toolchain_type",
     ],
     doc = """Builds a WebAssembly component from Go source using TinyGo + WASI Preview 2.
 

go/defs.bzl

@@ -211,6 +211,7 @@ bzl_library(
 file_ops_toolchain(
     name = "file_ops_toolchain_impl",
     file_ops_component = "//tools/file_ops:file_ops",
+    wasm_component = "@file_ops_component_external//file",
     wit_files = ["//tools/file_ops:wit_files"],
 )
 

toolchains/BUILD.bazel

@@ -9,9 +9,11 @@ def _file_ops_toolchain_impl(ctx):
 
     return [platform_common.ToolchainInfo(
         file_ops_component = ctx.executable.file_ops_component,
+        file_ops_wasm_component = ctx.file.wasm_component,
         file_ops_info = struct(
             component = ctx.executable.file_ops_component,
             wit_files = ctx.files.wit_files,
+            wasm_component = ctx.file.wasm_component,
         ),
     )]
 
@@ -24,6 +26,12 @@ file_ops_toolchain = rule(
             cfg = "exec",
             doc = "File Operations Component executable",
         ),
+        "wasm_component": attr.label(
+            mandatory = True,
+            allow_single_file = [".wasm"],
+            cfg = "exec",
+            doc = "WASM component file for file operations",
+        ),
         "wit_files": attr.label_list(
             allow_files = [".wit"],
             doc = "WIT interface files for the component",

toolchains/file_ops_toolchain.bzl

@@ -151,8 +151,14 @@ def prepare_workspace_action(ctx, config):
     file_ops_toolchain = ctx.toolchains["@rules_wasm_component//toolchains:file_ops_toolchain_type"]
     file_ops_tool = file_ops_toolchain.file_ops_component
 
+    # Get wasmtime and WASM component from toolchain
+    wasmtime_toolchain = ctx.toolchains["@rules_wasm_component//toolchains:wasmtime_toolchain_type"]
+    wasmtime_binary = wasmtime_toolchain.wasmtime
+
+    wasm_component = file_ops_toolchain.file_ops_wasm_component
+
     # Collect all input files and build operations list
-    all_inputs = []
+    all_inputs = [wasmtime_binary, wasm_component]
     operations = []
 
     # Process source files
@@ -208,9 +214,13 @@ def prepare_workspace_action(ctx, config):
         ])
 
     # Build JSON config for file operations tool
+    # Use absolute paths in the sandbox - wasmtime_binary and wasm_component are Files
+    # so we can get their paths relative to the execution root
     file_ops_config = {
-        "workspace_dir": workspace_dir.path,
+        "workspace_dir": workspace_dir.short_path,
         "operations": operations,
+        "wasmtime_path": wasmtime_binary.path,
+        "wasm_component_path": wasm_component.path,
     }
 
     # Write config to a JSON file
@@ -457,6 +467,7 @@ def setup_js_workspace_action(ctx, sources, package_json = None, npm_deps = None
         outputs = [workspace_dir],
         mnemonic = "SetupJSWorkspace",
         progress_message = "Setting up JavaScript workspace for %s" % ctx.label,
+        use_default_shell_env = True,  # Allow access to environment for runfiles discovery
     )
 
     return workspace_dir