chore(brain): remove brain_write legacy params domain/type/knowledge-path (ADR-0012)

hyperguild#79's caller audit (done in a prior session) found the removal
was safe:

- The promote/pending flow (#38/#81, ingestion/internal/api/promote.go)
  operates exclusively on brainDir/raw/ -> brainDir/wiki/<wing>/<hall>/. It
  never touches brainDir/knowledge/, so removing the knowledge/ write path
  does not break it.
- No live caller uses domain/type or the knowledge/ path: checked
  hyperguild itself, mathias/skills, mathias/agentsquad, mathias/dispatch,
  mathias/cad, mathias/cad-atlas.
- internal/skills/brain (a skill.go + handlers.go pair) defined a third,
  even-more-legacy brain_write shape (type/domain/filename, no wing/hall)
  for an old "supervisor" MCP server whose cmd/supervisor/main.go no
  longer exists. Nothing outside its own test imported it; deleted
  entirely as it encodes the exact legacy shape this issue removes.

Changes:
- ingestion/internal/mcp/handlers.go: brain_write's tool schema and
  brainWriteArgs drop type/domain; wing+hall are now marked required in
  the schema.
- ingestion/internal/api/handler.go: WriteNote has one behaviour — wing+
  hall required, routing to wiki/<wing>/<hall>/. writeLegacyNote and the
  knowledge/-path branch are deleted. Omitting wing or hall now returns
  "wing and hall are required" (400 over HTTP, a tool error over MCP) —
  the only sane failure mode left once there is no other valid
  destination.
- ingestion/internal/capture/ports.go, internal/brainstore/store.go: drop
  Type/Domain from capture.Note and its WriteNoteOptions construction.
  pipeline/*.go's unrelated "domain" field (a different, legitimate
  concept for brain_ingest_raw) is untouched.
- internal/skills/brain/: deleted (orphaned legacy tool schema, dead
  since cmd/supervisor was removed).

Tests: added TestWriteNote_RequiresWingAndHall (api),
TestBrainWriteRequiresWingAndHall +
TestBrainWriteIgnoresLegacyTypeAndDomainParams (mcp) for the new single
behaviour; removed tests that only exercised the deleted legacy path
(TestWrite_IncludesFrontmatterWhenTypeProvided,
TestWriteNote_HallRouteExistingTypeWinsOverOptsType,
TestBrainWriteRejectsTraversal, TestBrainWriteAcceptsDoubleDotInName —
the latter two's filename-sanitisation behaviour is covered independently
by internal/brain/path_test.go's TestNotePath_SanitisesWingAndSlug /
TestSanitise, which is unaffected by this change).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

ingestion/internal/api/handler_test.go

@@ -65,11 +65,13 @@ func TestQuery_ReturnsResults(t *testing.T) {
 	assert.NotEmpty(t, results)
 }
 
-func TestWrite_CreatesKnowledgeFile(t *testing.T) {
+func TestWrite_CreatesWikiFile(t *testing.T) {
 	dir, h := setup(t)
 	body, _ := json.Marshal(map[string]any{
 		"content":  "# Test note\n\nSome content.",
-		"filename": "test-note.md",
+		"filename": "test-note",
+		"wing":     "homelab",
+		"hall":     "facts",
 	})
 	req := httptest.NewRequest(http.MethodPost, "/write", bytes.NewReader(body))
 	rec := httptest.NewRecorder()
@@ -81,11 +83,25 @@ func TestWrite_CreatesKnowledgeFile(t *testing.T) {
 	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &resp))
 	assert.NotEmpty(t, resp["path"])
 
-	content, err := os.ReadFile(filepath.Join(dir, "knowledge", "test-note.md"))
+	content, err := os.ReadFile(filepath.Join(dir, "wiki", "homelab", "facts", "test-note.md"))
 	require.NoError(t, err)
 	assert.Contains(t, string(content), "Some content.")
 }
 
+// TestWrite_RequiresWingAndHall is the HTTP-contract counterpart of
+// TestWriteNote_RequiresWingAndHall: a caller (e.g. the MCP brain_write
+// handler) that omits wing/hall gets a 400, not a silent legacy write.
+func TestWrite_RequiresWingAndHall(t *testing.T) {
+	_, h := setup(t)
+	body, _ := json.Marshal(map[string]any{"content": "no destination"})
+	req := httptest.NewRequest(http.MethodPost, "/write", bytes.NewReader(body))
+	rec := httptest.NewRecorder()
+
+	h.Write(rec, req)
+
+	assert.Equal(t, http.StatusBadRequest, rec.Code)
+}
+
 func TestQuery_RequiresQuery(t *testing.T) {
 	_, h := setup(t)
 	body, _ := json.Marshal(map[string]any{"limit": 5})
@@ -97,27 +113,6 @@ func TestQuery_RequiresQuery(t *testing.T) {
 	assert.Equal(t, http.StatusBadRequest, rec.Code)
 }
 
-func TestWrite_IncludesFrontmatterWhenTypeProvided(t *testing.T) {
-	dir, h := setup(t)
-	body, _ := json.Marshal(map[string]any{
-		"content":  "Some learning.",
-		"filename": "typed-note.md",
-		"type":     "concept",
-		"domain":   "software",
-	})
-	req := httptest.NewRequest(http.MethodPost, "/write", bytes.NewReader(body))
-	rec := httptest.NewRecorder()
-
-	h.Write(rec, req)
-
-	assert.Equal(t, http.StatusOK, rec.Code)
-	content, err := os.ReadFile(filepath.Join(dir, "knowledge", "typed-note.md"))
-	require.NoError(t, err)
-	assert.Contains(t, string(content), "type: concept")
-	assert.Contains(t, string(content), "domain: software")
-	assert.Contains(t, string(content), "Some learning.")
-}
-
 func TestWriteNote_HallRouteIncludesSourceTypeWhenSet(t *testing.T) {
 	dir := t.TempDir()
 
@@ -126,7 +121,6 @@ func TestWriteNote_HallRouteIncludesSourceTypeWhenSet(t *testing.T) {
 		Filename:   "session-koala-abc",
 		Wing:       "claude-sessions",
 		Hall:       "facts",
-		Type:       "source",
 		SourceType: "internal",
 	})
 	require.NoError(t, err)
@@ -210,37 +204,51 @@ func TestWriteNote_HallRouteMergesExistingFrontmatterInsteadOfStacking(t *testin
 	assert.Contains(t, body, "# Body")
 }
 
-func TestWriteNote_HallRouteExistingTypeWinsOverOptsType(t *testing.T) {
-	dir := t.TempDir()
-
-	rel, err := api.WriteNote(dir, api.WriteNoteOptions{
-		Content:  "---\ntype: hypothesis\n---\n\nBody.\n",
-		Filename: "note",
-		Wing:     "agentsquad",
-		Hall:     "decisions",
-		Type:     "decision", // should lose to content's own "type: hypothesis"
-	})
-	require.NoError(t, err)
-
-	got, err := os.ReadFile(filepath.Join(dir, filepath.FromSlash(rel)))
-	require.NoError(t, err)
-	assert.Contains(t, string(got), "type: hypothesis")
-	assert.NotContains(t, string(got), "type: decision")
+// TestWriteNote_RequiresWingAndHall pins the post-legacy-removal contract
+// (hyperguild#79 / ADR-0012): with the knowledge/ fallback gone, wing+hall
+// is the only valid destination, so omitting either is a caller error, not
+// a silent fallback.
+func TestWriteNote_RequiresWingAndHall(t *testing.T) {
+	cases := []struct {
+		name string
+		wing string
+		hall string
+	}{
+		{"neither set", "", ""},
+		{"wing only", "homelab", ""},
+		{"hall only", "", "facts"},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			dir := t.TempDir()
+			_, err := api.WriteNote(dir, api.WriteNoteOptions{
+				Content: "body",
+				Wing:    tc.wing,
+				Hall:    tc.hall,
+			})
+			require.Error(t, err)
+			assert.Contains(t, err.Error(), "wing and hall are required")
+		})
+	}
 }
 
 func TestWrite_GeneratesFilenameIfAbsent(t *testing.T) {
 	dir, h := setup(t)
-	body, _ := json.Marshal(map[string]any{"content": "auto name"})
+	body, _ := json.Marshal(map[string]any{
+		"content": "auto name",
+		"wing":    "homelab",
+		"hall":    "facts",
+	})
 	req := httptest.NewRequest(http.MethodPost, "/write", bytes.NewReader(body))
 	rec := httptest.NewRecorder()
 
 	h.Write(rec, req)
 
 	assert.Equal(t, http.StatusOK, rec.Code)
-	entries, _ := os.ReadDir(filepath.Join(dir, "knowledge"))
-	// +1 because setup already wrote tdd.md
-	assert.Len(t, entries, 2)
-	assert.True(t, strings.HasSuffix(entries[1].Name(), ".md"))
+	entries, err := os.ReadDir(filepath.Join(dir, "wiki", "homelab", "facts"))
+	require.NoError(t, err)
+	require.Len(t, entries, 1)
+	assert.True(t, strings.HasSuffix(entries[0].Name(), ".md"))
 }
 
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