chore(lint): adopt the canonical .golangci.yml from infra/ci-templates

Canonical lives at infra ci-templates/golangci.yml, distributed by the
infra#309 pattern: byte-identical copies, checksum drift gate in infra. Do
not edit this file here -- edit the canonical and run `task ci:sync`.

Verified locally before pushing, not pushed-and-hoped: golangci-lint v2.11.4
against a Go 1.26.1 toolchain (matching CI) reports 0 issues here.

Also applies gofumpt, which this config enables and the golangci-lint v2
default set does not check at all. That gap is why the drift was invisible:
earlier passes ran gofmt, which is weaker. Mechanical, deterministic,
build+vet verified.

.golangci.yml

@@ -0,0 +1,52 @@
+# Canonical golangci-lint configuration for the estate's Go repos (infra#309
+# pattern: one canonical file here, a byte-identical copy in each adopter,
+# and the drift gate in THIS repo comparing sha256).
+#
+# Why this exists: 26 Go repos, 3 had a lint config, and all three were
+# different. The 23 without one ran golangci-lint's v2 default set, which
+# does NOT include a formatter -- so gofmt/gofumpt drift went uncaught until
+# it was found by hand (dma-cli#12: two files drifted, nothing flagged them).
+#
+# The two configs this replaces (cobalt-dingo, coo-agent) were near-identical
+# copies of each other AND both invalid under v2: they carried v1-style
+# `linters-settings` and `issues.exclude-rules` keys, which `golangci-lint
+# config verify` rejects outright. Their revive settings and test exclusions
+# were therefore not in effect. Consolidating fixes that too.
+#
+# Per-repo variation does NOT belong here -- this file must stay byte-identical
+# across adopters so the gate is a checksum, not a diff a human has to judge.
+# A repo with a genuine exception (agentsquad excludes its seeded-bug fixture
+# tree, which exists precisely to contain broken code) keeps its own config and
+# is not listed as an adopter.
+
+version: "2"
+
+linters:
+  default: none
+  enable:
+    - errcheck # unchecked errors
+    - govet # suspicious constructs
+    - staticcheck # broad static analysis
+    - unused # unused code
+    - misspell # spelling
+    - revive # idiomatic Go
+    - exhaustive # exhaustive switch on enums
+
+  settings:
+    revive:
+      rules:
+        - name: var-naming
+          severity: warning
+
+  exclusions:
+    rules:
+      # Test files: table-driven cases legitimately carry unused struct fields
+      # and long functions.
+      - path: _test\.go
+        linters:
+          - revive
+          - unused
+
+formatters:
+  enable:
+    - gofumpt

ingestion/internal/capturehttp/handler_test.go

@@ -38,9 +38,11 @@ func (f fakeTracker) CreateIssue(context.Context, string, string, string) (captu
 	}
 	return capture.IssueRef{Repo: "hyperguild", Number: 1, URL: "https://git/1"}, nil
 }
+
 func (fakeTracker) CloseIssue(context.Context, string, int, string) (capture.IssueRef, error) {
 	return capture.IssueRef{}, nil
 }
+
 func (fakeTracker) CommentIssue(context.Context, string, int, string) (capture.IssueRef, error) {
 	return capture.IssueRef{}, nil
 }
@@ -183,6 +185,7 @@ type refusingAudit struct{}
 func (refusingAudit) Reserve(context.Context, classification.Level) (capture.AuditOutcome, error) {
 	return 0, errors.New("central audit sink unreachable")
 }
+
 func (refusingAudit) Record(context.Context, capture.AuditEntry, capture.AuditOutcome) error {
 	return nil
 }

ingestion/internal/mcp/server_test.go

@@ -134,9 +134,11 @@ type stubTracker struct{}
 func (stubTracker) CreateIssue(context.Context, string, string, string) (capture.IssueRef, error) {
 	return capture.IssueRef{}, nil
 }
+
 func (stubTracker) CloseIssue(context.Context, string, int, string) (capture.IssueRef, error) {
 	return capture.IssueRef{}, nil
 }
+
 func (stubTracker) CommentIssue(context.Context, string, int, string) (capture.IssueRef, error) {
 	return capture.IssueRef{}, nil
 }

ingestion/internal/mcp/tools_capture_test.go

@@ -28,9 +28,11 @@ type capFakeTracker struct{}
 func (capFakeTracker) CreateIssue(context.Context, string, string, string) (capture.IssueRef, error) {
 	return capture.IssueRef{Repo: "hyperguild", Number: 1, URL: "https://git/1"}, nil
 }
+
 func (capFakeTracker) CloseIssue(context.Context, string, int, string) (capture.IssueRef, error) {
 	return capture.IssueRef{}, nil
 }
+
 func (capFakeTracker) CommentIssue(context.Context, string, int, string) (capture.IssueRef, error) {
 	return capture.IssueRef{}, nil
 }

ingestion/internal/startupretry/startupretry_test.go

@@ -18,7 +18,6 @@ func TestDo_ReturnsImmediatelyOnFirstSuccess(t *testing.T) {
 		calls++
 		return "ready", nil
 	})
-
 	if err != nil {
 		t.Fatalf("Do: %v", err)
 	}
@@ -41,7 +40,6 @@ func TestDo_SurvivesTransientFailuresThenSucceeds(t *testing.T) {
 		}
 		return "ready", nil
 	})
-
 	if err != nil {
 		t.Fatalf("Do returned %v — a transient 502 must not be fatal", err)
 	}

internal/config/models_test.go

@@ -30,7 +30,7 @@ skills:
 func writeModels(t *testing.T, content string) string {
 	t.Helper()
 	f := filepath.Join(t.TempDir(), "models.yaml")
-	require.NoError(t, os.WriteFile(f, []byte(content), 0644))
+	require.NoError(t, os.WriteFile(f, []byte(content), 0o644))
 	return f
 }
 

internal/registry/registry_test.go

@@ -22,6 +22,7 @@ func (s stubSkill) Tools() []registry.ToolDef {
 		InputSchema: json.RawMessage(`{"type":"object","properties":{}}`),
 	}}
 }
+
 func (s stubSkill) Handle(ctx context.Context, tool string, args json.RawMessage) (json.RawMessage, error) {
 	return json.RawMessage(`{"ok":true}`), nil
 }