feat(capturehttp): POST /capture REST adapter + OAuth2 + origin resolver (#53)

The HTTP door for the capture capability. Thin: authenticate → derive
trust-zone origin → decode → capture.Service → map receipt to status.

- Auth mirrors the chassis Bearer precedence (static token wins, then Dex
  JWT) but returns the resolved principal + auth path, which the chassis
  middleware hides — capture needs the principal to derive the origin.
  Depends on a small Validator interface (the chassis *JWTValidator
  satisfies it) so the JWT/origin path is testable without a live JWKS.
- OriginResolver maps principal → trust zone: static-token caller and
  allowlisted JWT subjects → sovereign; every other principal → us-nexus
  (fail safe, so the I1 gate refuses confidential by default). Principal
  and origin are server-set on the input, overwriting any body the caller
  sent.
- HTTP status: 200 all-ok / dry-run, 207 partial, 502 all-failed, 403 on
  the I1 refusal, 400 on fail-closed validation.
- Wired in main behind the same static+JWT credentials as /mcp, reusing
  the MCP server's graph-wired brain store (one implementation) and the
  classification tags (#50). Mounts only when a Gitea tracker is
  configured. Sovereign JWT principals via BRAIN_CAPTURE_SOVEREIGN_PRINCIPALS.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ingestion/cmd/server/main.go

@@ -16,6 +16,10 @@ import (
 
 	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/claudewatcher"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/audit"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/capture"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/capturehttp"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/classification"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/embed"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/gitea"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/graphstore"
@@ -119,6 +123,18 @@ func envInt(key string, fallback int) int {
 	return fallback
 }
 
+// splitList parses a comma-separated env value into a trimmed,
+// empty-free slice. Used for the capture sovereign-principal allowlist.
+func splitList(v string) []string {
+	var out []string
+	for _, p := range strings.Split(v, ",") {
+		if p = strings.TrimSpace(p); p != "" {
+			out = append(out, p)
+		}
+	}
+	return out
+}
+
 // systemHostname returns os.Hostname() with a "unknown" fallback so the
 // caller never has to handle the rare error path.
 func systemHostname() string {
@@ -349,6 +365,30 @@ func main() {
 
 	mux.Handle("/mcp", chassisauth.BearerMiddleware(mcpToken, jwtValidator, "brain", resourceMetadataURL, mcpSrv))
 
+	// POST /capture (#53): the uniform capture REST door. Needs a ticket
+	// tracker to file action items, so it only mounts when Gitea is
+	// configured. It reuses the MCP server's graph-wired brain store (one
+	// implementation), the classification tags for the I1 gate, and a slog
+	// audit sink (the loki+buffer sink lands in #54). The handler does its
+	// own auth (static + JWT) because it needs the principal to derive the
+	// trust-zone origin — the chassis middleware hides it.
+	if tracker := mcpSrv.IssueTracker(); tracker != nil {
+		classCfg, cerr := classification.Load(brainDir)
+		if cerr != nil {
+			logger.Error("load classification config", "err", cerr)
+			os.Exit(1)
+		}
+		captureSvc := capture.NewService(
+			mcpSrv.BrainStore(), tracker, nil, classCfg, audit.NewSlogSink(logger))
+		sovereign := splitList(os.Getenv("BRAIN_CAPTURE_SOVEREIGN_PRINCIPALS"))
+		captureH := capturehttp.New(captureSvc, jwtValidator, mcpToken, "local-cli",
+			capturehttp.NewOriginResolver(sovereign))
+		mux.Handle("POST /capture", captureH)
+		logger.Info("capture endpoint enabled", "sovereign_principals", len(sovereign))
+	} else {
+		logger.Info("capture endpoint disabled (BRAIN_GITEA_TOKEN unset)")
+	}
+
 	// Opt-in OAuth 2.0 client_credentials flow for claude.ai's custom-MCP
 	// integration UI, which has no static-Bearer field. Setting both
 	// OAUTH_CLIENT_ID and OAUTH_CLIENT_SECRET enables the token exchange;