feat(tools): add WebFetch and WebSearch parity primitives

Implement the first web-oriented Claude Code parity slice in the Rust tools crate. This adds concrete WebFetch and WebSearch tool specs, execution paths, lightweight HTML/search-result extraction, domain filtering, and local HTTP-backed tests while leaving the existing core file and shell tools intact.\n\nConstraint: Keep the change scoped to tools-only Rust workspace code\nConstraint: Match Claude Code tool names and JSON schemas closely enough for parity work\nRejected: Stub-only tool registrations | would not materially expand beyond MVP\nRejected: Full browser/search service integration | too large for this first logical slice\nConfidence: medium\nScope-risk: moderate\nReversibility: clean\nDirective: Treat these web helpers as a parity foundation; refine result quality without renaming the exposed tool contracts\nTested: cargo fmt; cargo test -p tools\nNot-tested: cargo clippy; full workspace cargo test

rust/Cargo.lock

@@ -212,6 +212,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "07bbe89c50d7a535e539b8c17bc0b49bdb77747034daa8087407d655f3f7cc1d"
 dependencies = [
  "futures-core",
+ "futures-sink",
 ]
 
 [[package]]
@@ -220,6 +221,18 @@ version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7e3450815272ef58cec6d564423f6e755e25379b217b0bc688e295ba24df6b1d"
 
+[[package]]
+name = "futures-io"
+version = "0.3.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cecba35d7ad927e23624b22ad55235f2239cfa44fd10428eecbeba6d6a717718"
+
+[[package]]
+name = "futures-sink"
+version = "0.3.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c39754e157331b013978ec91992bde1ac089843443c49cbc7f46150b0fad0893"
+
 [[package]]
 name = "futures-task"
 version = "0.3.32"
@@ -233,7 +246,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "389ca41296e6190b48053de0321d02a77f32f8a5d2461dd38762c0593805c6d6"
 dependencies = [
  "futures-core",
+ "futures-io",
+ "futures-sink",
  "futures-task",
+ "memchr",
  "pin-project-lite",
  "slab",
 ]
@@ -898,7 +914,9 @@ checksum = "eddd3ca559203180a307f12d114c268abf583f59b03cb906fd0b3ff8646c1147"
 dependencies = [
  "base64",
  "bytes",
+ "futures-channel",
  "futures-core",
+ "futures-util",
  "http",
  "http-body",
  "http-body-util",
@@ -1352,6 +1370,7 @@ dependencies = [
 name = "tools"
 version = "0.1.0"
 dependencies = [
+ "reqwest",
  "runtime",
  "serde",
  "serde_json",