Add repo-detail panel and /api/repo endpoint

New <repo-detail> component listens for repo:select and shows a repo's remotes, local branches (current + upstream), and recent commits. Backed by GET /api/repo (restricted to indexed repos) and read-only git readers LocalBranches/RecentCommits/RemoteDetails via repos.BuildDetail. <repo-list> highlights the selection; page docks the two panels left/right.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/git/git.go

@@ -119,3 +119,106 @@ func (c *CLI) Fetch(ctx context.Context, dir string) error {
 	_, err := c.run(ctx, dir, "fetch", "--quiet", "--all")
 	return err
 }
+
+// Branch is a local branch and its upstream, if any.
+type Branch struct {
+	Name     string `json:"name"`
+	Current  bool   `json:"current"`
+	Upstream string `json:"upstream,omitempty"`
+}
+
+// Commit is a single log entry.
+type Commit struct {
+	Short   string `json:"short"`
+	Author  string `json:"author"`
+	Date    string `json:"date"`
+	Subject string `json:"subject"`
+}
+
+// Remote is a named remote and its fetch URL.
+type Remote struct {
+	Name string `json:"name"`
+	URL  string `json:"url"`
+}
+
+// LocalBranches lists local branches (refs/heads), flagging the current one and
+// including each branch's upstream when set.
+func (c *CLI) LocalBranches(ctx context.Context, dir string) ([]Branch, error) {
+	const format = "%(refname:short)%09%(HEAD)%09%(upstream:short)"
+	out, err := c.run(ctx, dir, "for-each-ref", "--format="+format, "refs/heads")
+	if err != nil {
+		return nil, err
+	}
+	var branches []Branch
+	for _, line := range splitLines(out) {
+		f := strings.Split(line, "\t")
+		if len(f) < 1 || f[0] == "" {
+			continue
+		}
+		b := Branch{Name: f[0]}
+		if len(f) > 1 {
+			b.Current = f[1] == "*"
+		}
+		if len(f) > 2 {
+			b.Upstream = f[2]
+		}
+		branches = append(branches, b)
+	}
+	return branches, nil
+}
+
+// RecentCommits returns the newest n commits reachable from HEAD.
+func (c *CLI) RecentCommits(ctx context.Context, dir string, n int) ([]Commit, error) {
+	// Fields separated by TAB (%x09); records by newline.
+	const format = "%h%x09%an%x09%ad%x09%s"
+	out, err := c.run(ctx, dir, "log", "-n", strconv.Itoa(n), "--date=short", "--pretty=format:"+format)
+	if err != nil {
+		return nil, err
+	}
+	var commits []Commit
+	for _, line := range splitLines(out) {
+		f := strings.SplitN(line, "\t", 4)
+		if len(f) < 4 {
+			continue
+		}
+		commits = append(commits, Commit{Short: f[0], Author: f[1], Date: f[2], Subject: f[3]})
+	}
+	return commits, nil
+}
+
+// RemoteDetails returns each remote with its fetch URL.
+func (c *CLI) RemoteDetails(ctx context.Context, dir string) ([]Remote, error) {
+	out, err := c.run(ctx, dir, "remote", "-v")
+	if err != nil {
+		return nil, err
+	}
+	seen := make(map[string]struct{})
+	var remotes []Remote
+	for _, line := range splitLines(out) {
+		// Format: "<name>\t<url> (fetch|push)"
+		f := strings.Fields(line)
+		if len(f) < 3 || f[2] != "(fetch)" {
+			continue
+		}
+		if _, ok := seen[f[0]]; ok {
+			continue
+		}
+		seen[f[0]] = struct{}{}
+		remotes = append(remotes, Remote{Name: f[0], URL: f[1]})
+	}
+	return remotes, nil
+}
+
+// splitLines splits on newlines, dropping empty lines.
+func splitLines(s string) []string {
+	if s == "" {
+		return nil
+	}
+	var out []string
+	for _, line := range strings.Split(s, "\n") {
+		if line != "" {
+			out = append(out, line)
+		}
+	}
+	return out
+}

internal/repos/detail.go

@@ -0,0 +1,56 @@
+package repos
+
+import (
+	"context"
+	"time"
+
+	"gitmanager/internal/git"
+)
+
+// Detail is the enriched view of a single repository shown in the detail panel.
+// It embeds the cached State and adds data fetched on demand via the git
+// boundary (all read-only — AGENT.md §1.3).
+type Detail struct {
+	State
+	Branches      []git.Branch `json:"branches"`
+	Commits       []git.Commit `json:"commits"`
+	RemoteDetails []git.Remote `json:"remoteDetails"`
+}
+
+// Get returns the cached State for a repo path, or false if it is not indexed.
+func (i *Index) Get(path string) (State, bool) {
+	i.mu.RLock()
+	defer i.mu.RUnlock()
+	s, ok := i.byKey[path]
+	return s, ok
+}
+
+// BuildDetail enriches a cached State with branches, recent commits, and remote
+// URLs. Errors on the enriching calls are non-fatal: whatever succeeds is
+// returned, and the partial failure is recorded on Detail.Error.
+func BuildDetail(ctx context.Context, g *git.CLI, base State) Detail {
+	ctx, cancel := context.WithTimeout(ctx, 20*time.Second)
+	defer cancel()
+
+	d := Detail{State: base}
+
+	if branches, err := g.LocalBranches(ctx, base.Path); err == nil {
+		d.Branches = branches
+	} else {
+		d.Error = err.Error()
+	}
+
+	if commits, err := g.RecentCommits(ctx, base.Path, 20); err == nil {
+		d.Commits = commits
+	} else if d.Error == "" {
+		d.Error = err.Error()
+	}
+
+	if remotes, err := g.RemoteDetails(ctx, base.Path); err == nil {
+		d.RemoteDetails = remotes
+	} else if d.Error == "" {
+		d.Error = err.Error()
+	}
+
+	return d
+}