feat: Add hooks, workflow, MCP support and core modules

Phase 2: Hooks System
- Event-driven execution with HookEvent/HookAction types
- HookManager for registration and execution

Phase 3: Multi-Agent Workflow
- Workflow orchestration with dependency graphs
- WorkflowStep with conditions and retry support

Phase 4: MCP (Model Context Protocol) Support
- McpServer for external tool servers
- McpManager for multiple server management

Also includes core modules: cache, error_policy, feature_flags,
git, logger, plugin, retry, rules

662 tests passing

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

Co-Authored-By: Claude <noreply@anthropic.com>

Cargo.lock

@@ -198,6 +198,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cd405d82c84ff7f35739f175f67d8b9fb7687a0e84ccdc78bd3568839827cf07"
 dependencies = [
  "find-msvc-tools",
+ "jobserver",
+ "libc",
  "shlex",
 ]
 
@@ -745,6 +747,21 @@ dependencies = [
  "wasip2",
 ]
 
+[[package]]
+name = "git2"
+version = "0.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b903b73e45dc0c6c596f2d37eccece7c1c8bb6e4407b001096387c63d0d93724"
+dependencies = [
+ "bitflags",
+ "libc",
+ "libgit2-sys",
+ "log",
+ "openssl-probe",
+ "openssl-sys",
+ "url",
+]
+
 [[package]]
 name = "glob"
 version = "0.3.3"
@@ -1139,6 +1156,16 @@ version = "1.0.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4a5f13b858c8d314ee3e8f639011f7ccefe71f97f96e50151fb991f267928e2c"
 
+[[package]]
+name = "jobserver"
+version = "0.1.34"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9afb3de4395d6b3e67a780b6de64b51c978ecf11cb9a462c66be7d4ca9039d33"
+dependencies = [
+ "getrandom 0.3.4",
+ "libc",
+]
+
 [[package]]
 name = "js-sys"
 version = "0.3.82"
@@ -1161,6 +1188,20 @@ version = "0.2.177"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2874a2af47a2325c2001a6e6fad9b16a53b802102b528163885171cf92b15976"
 
+[[package]]
+name = "libgit2-sys"
+version = "0.17.0+1.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "10472326a8a6477c3c20a64547b0059e4b0d086869eee31e6d7da728a8eb7224"
+dependencies = [
+ "cc",
+ "libc",
+ "libssh2-sys",
+ "libz-sys",
+ "openssl-sys",
+ "pkg-config",
+]
+
 [[package]]
 name = "libredox"
 version = "0.1.10"
@@ -1171,6 +1212,32 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "libssh2-sys"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "220e4f05ad4a218192533b300327f5150e809b54c4ec83b5a1d91833601811b9"
+dependencies = [
+ "cc",
+ "libc",
+ "libz-sys",
+ "openssl-sys",
+ "pkg-config",
+ "vcpkg",
+]
+
+[[package]]
+name = "libz-sys"
+version = "1.1.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "15d118bbf3771060e7311cc7bb0545b01d08a8b4a7de949198dec1fa0ca1c0f7"
+dependencies = [
+ "cc",
+ "libc",
+ "pkg-config",
+ "vcpkg",
+]
+
 [[package]]
 name = "linked-hash-map"
 version = "0.5.6"
@@ -1293,16 +1360,19 @@ dependencies = [
  "chrono",
  "dirs",
  "futures",
+ "git2",
  "glob",
  "regex",
  "reqwest",
  "serde",
  "serde_json",
+ "serde_yaml",
  "tempfile",
  "thiserror 2.0.17",
  "tokio",
  "toml",
  "tracing",
+ "tracing-subscriber",
  "uuid",
 ]
 
@@ -2007,6 +2077,19 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "serde_yaml"
+version = "0.9.34+deprecated"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a8b1a1a2ebf674015cc02edccce75287f1a0130d394307b36743c2f5d504b47"
+dependencies = [
+ "indexmap",
+ "itoa",
+ "ryu",
+ "serde",
+ "unsafe-libyaml",
+]
+
 [[package]]
 name = "sharded-slab"
 version = "0.1.7"
@@ -2522,6 +2605,16 @@ dependencies = [
  "tracing-core",
 ]
 
+[[package]]
+name = "tracing-serde"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "704b1aeb7be0d0a84fc9828cae51dab5970fee5088f83d1dd7ee6f6246fc6ff1"
+dependencies = [
+ "serde",
+ "tracing-core",
+]
+
 [[package]]
 name = "tracing-subscriber"
 version = "0.3.20"
@@ -2532,12 +2625,15 @@ dependencies = [
  "nu-ansi-term",
  "once_cell",
  "regex-automata",
+ "serde",
+ "serde_json",
  "sharded-slab",
  "smallvec",
  "thread_local",
  "tracing",
  "tracing-core",
  "tracing-log",
+ "tracing-serde",
 ]
 
 [[package]]
@@ -2593,6 +2689,12 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1fc81956842c57dac11422a97c3b8195a1ff727f06e85c84ed2e8aa277c9a0fd"
 
+[[package]]
+name = "unsafe-libyaml"
+version = "0.2.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "673aac59facbab8a9007c7f6108d11f63b603f7cabff99fabf650fea5c32b861"
+
 [[package]]
 name = "untrusted"
 version = "0.9.0"