feat(ginit): 新增一键初始化本地 Git 仓库命令

`quicommit ginit`（别名 `gi`）离线完成仓库起步：用 git2 建库并确立初始分支、
写最简 README.md、按根目录标志文件装配 .gitignore、按 --add 添加远程，
`--profile` 可选套用已有 Git 配置。在已有仓库上重复执行只补齐缺失项：绝不覆盖
既有的 README.md/.gitignore、绝不改动已有 remote 的地址、不提供 --force、
不创建首个提交。边界取舍见 ADR 0006，命令命名见 ADR 0005。

实现落在新的 src/git/init.rs（9 个 git 层函数）与 src/commands/ginit.rs，
命令层不直接引用 git2，GitRepo 公开接口未改动，其余命令行为不变。
测试：src/git/init.rs 11 条单元测试、tests/ginit_tests.rs 18 条集成测试；
新增 35 个 ginit_* 消息覆盖 7 种语言。

另将 CONTEXT.md 与 docs/adr/ 纳入版本跟踪（.gitignore 放开 adr/ 与
CONTEXT.md 两条忽略规则）；RAODMAP.md 除 ginit 条目外还包含此前未提交的
规划条目更新。

docs/adr/0002-llm-providers-on-rig.md

@@ -0,0 +1,7 @@
+# LLM provider layer built on rig-core instead of hand-written clients
+
+QuiCommit's LLM layer (commit/tag/changelog generation) moved from six hand-written HTTP clients to `rig-core` 0.41 (locked, `reqwest` + `rustls` features only, umbrella `rig` crate not used). Rationale: the hand-written layer accumulated duplicated SSE parsing, string-matching retry logic, inconsistent per-provider timeouts, and provider-specific bugs (Anthropic silently ignoring configured base_url, Ollama constructor panics); rig-core 0.41 natively supports all six providers and models reasoning/thinking as first-class typed content (streaming `Reasoning`/`ReasoningDelta` events), which matches QuiCommit's thinking-mode display feature. In exchange we accept rig's 0.x breaking-change velocity (upgrades require manual provider-diff review), no application-level retry on non-streaming requests, and the Ollama endpoint moving to `/api/chat`.
+
+**Considered Options**: keep hand-writing (rejected — every new provider meant a full HTTP/SSE/retry suite; six near-duplicate implementations already); per-provider SDKs like async-openai plus hand-written rest (rejected — multiple API styles, no unified interface); rig-core (accepted — one dependency covers every current provider and normalizes reasoning content across them).
+
+**Consequences**: user-visible behavior changes recorded in CHANGELOG for 0.6.0 (Ollama `/api/chat`, no non-streaming retry, credential-verify endpoint changes, Anthropic base_url now honored); rig-core upgrades must re-verify provider API changes before bumping the locked version.