docs(topics): Add topics section with Traversing Git Repos guide

why: Provide high-level conceptual documentation with runnable examples
what:
- Create docs/topics/ directory with index.md
- Add traversing_git.md explaining Manager/Cmd pattern for navigating
  git's object graph with typed Python objects
- All doctests verified passing

Author: tony

docs/index.md

@@ -9,6 +9,7 @@
 :hidden:
 
 quickstart
+topics/index
 url/index
 cmd/index
 sync/index

docs/topics/index.md

@@ -0,0 +1,15 @@
+---
+orphan: true
+---
+
+# Topics
+
+Explore libvcs's core functionalities and design patterns at a high level,
+with detailed explanations and runnable examples.
+
+```{toctree}
+
+traversing_git
+filtering
+url_parsing
+```

docs/topics/traversing_git.md

@@ -0,0 +1,150 @@
+(traversing-git-repos)=
+
+# Traversing Git Repos
+
+libvcs provides **Manager** and **Cmd** classes for navigating the "object graph"
+of your git repository. These aren't just convenient abstractions—they're also
+simulacra of the git commands themselves, giving you typed Python objects instead
+of raw strings.
+
+## Overview
+
+The pattern consists of two types of classes:
+
+- **Manager** classes handle collection-level operations (`ls()`, `get()`,
+  `filter()`, `add()`/`create()`)
+- **Cmd** classes handle per-entity operations (`show()`, `remove()`,
+  `rename()`)
+
+```
+Git instance
+├── branches: GitBranchManager
+│   ├── ls() -> QueryList[GitBranchCmd]
+│   ├── get() -> GitBranchCmd
+│   └── create()
+├── tags: GitTagManager
+├── remotes: GitRemoteManager
+├── stashes: GitStashManager
+├── worktrees: GitWorktreeManager
+├── notes: GitNotesManager
+├── submodules: GitSubmoduleManager
+└── reflog: GitReflogManager
+```
+
+## Basic Usage
+
+```python
+>>> from libvcs.cmd.git import Git
+>>> git = Git(path=example_git_repo.path)
+```
+
+### Listing Items
+
+All Manager classes have an `ls()` method that returns a
+{class}`~libvcs._internal.query_list.QueryList`:
+
+```python
+>>> from libvcs.cmd.git import Git
+>>> git = Git(path=example_git_repo.path)
+>>> branches = git.branches.ls()
+>>> isinstance(branches, list)
+True
+>>> tags = git.tags.ls()
+>>> remotes = git.remotes.ls()
+```
+
+### Getting a Single Item
+
+Use `get()` with filter criteria to retrieve a single item:
+
+```python
+>>> from libvcs.cmd.git import Git
+>>> git = Git(path=example_git_repo.path)
+>>> git.tags.create(name='v1.0.0', message='Release 1.0')
+''
+>>> tag = git.tags.get(tag_name='v1.0.0')
+>>> tag.tag_name
+'v1.0.0'
+```
+
+### Creating Items
+
+Manager classes provide `create()` or `add()` methods:
+
+```python
+>>> from libvcs.cmd.git import Git
+>>> git = Git(path=example_git_repo.path)
+>>> git.tags.create(name='v2.0.0', message='Release 2.0')
+''
+>>> git.branches.create(branch='feature-branch')
+''
+```
+
+### Per-Entity Operations
+
+Cmd objects have methods for mutating or inspecting that entity:
+
+```python
+>>> from libvcs.cmd.git import Git
+>>> git = Git(path=example_git_repo.path)
+>>> git.tags.create(name='v3.0.0', message='Release 3.0')
+''
+>>> tag = git.tags.get(tag_name='v3.0.0')
+>>> tag.delete()  # doctest: +ELLIPSIS
+"Deleted tag 'v3.0.0' ..."
+>>> git.branches.create(branch='temp-branch')
+''
+>>> branch = git.branches.get(branch_name='temp-branch')
+>>> branch.delete()  # doctest: +ELLIPSIS
+'Deleted branch temp-branch ...'
+```
+
+## Comparison to Raw Commands
+
+### Before: Parsing Strings
+
+Without the Manager/Cmd pattern, you'd parse raw output:
+
+```python
+>>> from libvcs.cmd.git import Git
+>>> git = Git(path=example_git_repo.path)
+>>> # Raw output requires parsing
+>>> raw_output = git.run(['tag', '-l'])
+>>> tag_names = [t for t in raw_output.strip().split('\\n') if t]
+```
+
+### After: Typed Objects
+
+With the Manager/Cmd pattern, you get typed objects:
+
+```python
+>>> from libvcs.cmd.git import Git
+>>> git = Git(path=example_git_repo.path)
+>>> tags = git.tags.ls()
+>>> for tag in tags:  # doctest: +SKIP
+...     print(f"{tag.tag_name}")
+```
+
+## When to Use
+
+| Use Case | Approach |
+|----------|----------|
+| List/filter/get entities | Manager class (`git.branches.ls()`) |
+| Mutate a specific entity | Cmd class (`branch.delete()`) |
+| Run arbitrary git commands | Direct methods (`git.run([...])`) |
+| Complex pipelines | Mix of both |
+
+## Available Managers
+
+| Manager | Access | Operations |
+|---------|--------|------------|
+| {class}`~libvcs.cmd.git.GitBranchManager` | `git.branches` | List, create, checkout branches |
+| {class}`~libvcs.cmd.git.GitTagManager` | `git.tags` | List, create tags |
+| {class}`~libvcs.cmd.git.GitRemoteManager` | `git.remotes` | List, add, configure remotes |
+| {class}`~libvcs.cmd.git.GitStashManager` | `git.stashes` | List, push, clear stashes |
+| {class}`~libvcs.cmd.git.GitWorktreeManager` | `git.worktrees` | List, add, prune worktrees |
+| {class}`~libvcs.cmd.git.GitNotesManager` | `git.notes` | List, add, prune notes |
+| {class}`~libvcs.cmd.git.GitSubmoduleManager` | `git.submodules` | List, add, sync submodules |
+| {class}`~libvcs.cmd.git.GitReflogManager` | `git.reflog` | List, expire reflog entries |
+
+See {doc}`/cmd/git/index` for the complete API reference.