feat: skills import — 从其他工具复制 Skills 的交互式 TUI

新增:
- skills_importer.rs: 扫描已知路径 (Claude Code, Agent Skills,
  OpenCode, pi) 发现可导入的 Skill
- ias skills list: 列出可导入的 Skill
- ias skills import: 交互式多选 TUI (dialoguer MultiSelect)
  复制选中的 Skill 到 skills/ 目录

依赖: dialoguer + console + dirs

Cargo.lock

@@ -402,6 +402,18 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "console"
+version = "0.16.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d64e8af5551369d19cf50138de61f1c42074ab970f74e99be916646777f8fc87"
+dependencies = [
+ "encode_unicode",
+ "libc",
+ "unicode-width 0.2.2",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "const-oid"
 version = "0.9.6"
@@ -546,6 +558,18 @@ dependencies = [
  "powerfmt",
 ]
 
+[[package]]
+name = "dialoguer"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "25f104b501bf2364e78d0d3974cbc774f738f5865306ed128e1e0d7499c0ad96"
+dependencies = [
+ "console",
+ "shell-words",
+ "tempfile",
+ "zeroize",
+]
+
 [[package]]
 name = "digest"
 version = "0.10.7"
@@ -558,6 +582,27 @@ dependencies = [
  "subtle",
 ]
 
+[[package]]
+name = "dirs"
+version = "6.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3e8aa94d75141228480295a7d0e7feb620b1a5ad9f12bc40be62411e38cce4e"
+dependencies = [
+ "dirs-sys",
+]
+
+[[package]]
+name = "dirs-sys"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e01a3366d27ee9890022452ee61b2b63a67e6f13f58900b651ff5665f0bb1fab"
+dependencies = [
+ "libc",
+ "option-ext",
+ "redox_users",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "displaydoc"
 version = "0.2.6"
@@ -584,6 +629,12 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "encode_unicode"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34aa73646ffb006b8f5147f3dc182bd4bcb190227ce861fc4a4844bf8e3cb2c0"
+
 [[package]]
 name = "encoding_rs"
 version = "0.8.35"
@@ -1131,6 +1182,9 @@ dependencies = [
  "base64",
  "chrono",
  "clap",
+ "console",
+ "dialoguer",
+ "dirs",
  "dotenvy",
  "futures-util",
  "hex",
@@ -1784,6 +1838,12 @@ dependencies = [
  "vcpkg",
 ]
 
+[[package]]
+name = "option-ext"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "04744f49eae99ab78e0d5c0b603ab218f515ea8cfe5a456d7629ad883a3b6e7d"
+
 [[package]]
 name = "parking"
 version = "2.2.1"
@@ -2162,6 +2222,17 @@ dependencies = [
  "bitflags",
 ]
 
+[[package]]
+name = "redox_users"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4e608c6638b9c18977b00b475ac1f28d14e84b27d8d42f70e0bf1e3dec127ac"
+dependencies = [
+ "getrandom 0.2.17",
+ "libredox",
+ "thiserror",
+]
+
 [[package]]
 name = "regex-automata"
 version = "0.4.14"
@@ -2331,7 +2402,7 @@ dependencies = [
  "nix",
  "radix_trie",
  "unicode-segmentation",
- "unicode-width",
+ "unicode-width 0.1.14",
  "utf8parse",
  "windows-sys 0.52.0",
 ]
@@ -2472,6 +2543,12 @@ dependencies = [
  "lazy_static",
 ]
 
+[[package]]
+name = "shell-words"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dc6fe69c597f9c37bfeeeeeb33da3530379845f10be461a66d16d03eca2ded77"
+
 [[package]]
 name = "shlex"
 version = "1.3.0"
@@ -3196,6 +3273,12 @@ version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7dd6e30e90baa6f72411720665d41d89b9a3d039dc45b8faea1ddd07f617f6af"
 
+[[package]]
+name = "unicode-width"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b4ac048d71ede7ee76d585517add45da530660ef4390e49b098733c6e897f254"
+
 [[package]]
 name = "unicode-xid"
 version = "0.2.6"