feat(vcs): complete Phase 1 — util.go, type cleanup, interface additions (fixes #84, #85, #86)

- Create vcs/util.go with GetAllFilesInPath and BuildLineToPositionMap
- Create vcs/util_test.go with comprehensive tests for both functions
- Remove review.ContentEntry type, replace with vcs.ContentEntry
- Remove review.GiteaClient interface, replace with vcs.FileReader
- Update review/repo_persona.go to use vcs.FileReader
- Update review/repo_persona_test.go to use vcs.ContentEntry
- Update cmd/review-bot/main.go adapter to implement vcs.FileReader
- Add Number and Base fields to vcs.PullRequest
- Add CommitStatus type to vcs/types.go
- Add GetFileContentAtRef to vcs.PRReader interface
- Add GetCommitStatuses to vcs.PRReader interface
- Add DismissReview to vcs.Reviewer interface
- Add stub implementations on gitea.Client for new interface methods

Closes #84, Closes #85, Closes #86

vcs/types.go

@@ -15,6 +15,11 @@ const (
 	ReviewEventComment ReviewEvent = "COMMENT"
 )
 
+// BaseRef identifies the target branch of a pull request.
+type BaseRef struct {
+	Ref string `json:"ref"`
+}
+
 // HeadRef identifies the source branch and latest commit of a pull request.
 type HeadRef struct {
 	SHA string `json:"sha"`
@@ -28,9 +33,11 @@ type UserInfo struct {
 
 // PullRequest holds relevant PR metadata.
 type PullRequest struct {
-	Title string  `json:"title"`
-	Body  string  `json:"body"`
-	Head  HeadRef `json:"head"`
+	Number int     `json:"number"`
+	Title  string  `json:"title"`
+	Body   string  `json:"body"`
+	Head   HeadRef `json:"head"`
+	Base   BaseRef `json:"base"`
 }
 
 // ChangedFile represents a file modified in a PR.
@@ -46,6 +53,14 @@ type ContentEntry struct {
 	Type string `json:"type"` // "file" or "dir"
 }
 
+// CommitStatus represents a single CI status entry for a commit.
+type CommitStatus struct {
+	Status      string `json:"status"`
+	Context     string `json:"context"`
+	Description string `json:"description"`
+	TargetURL   string `json:"target_url"`
+}
+
 // Review represents a pull request review.
 type Review struct {
 	ID       int64    `json:"id"`