Generalize the focus controller into a harness hosting swappable modes

Loosen AntiDrift's session controller into Keel's general collect→brain→act
loop. A new internal/harness runs at most one mode.Mode at a time, fanning
async completions out to the web SSE and status-bar surfaces.

- internal/mode: the Mode contract (Kind/Command/View/Active) plus optional
  EvidenceConsumer and Expirer ports, and the surfacing Envelope.
- internal/mode/focus: the former session/domain/statemachine packages moved
  under the mode, now satisfying the harness contracts unchanged.
- internal/mode/offscreen: a one-shot away-from-desk mode built on the new
  ai.Proposer, which turns a life-domain brief into one off-screen action.
- cmd/keeld replaces cmd/antidriftd; daemon wires focus + offscreen factories
  with per-mode persistence under ~/.keel/modes/<kind>.
- Finish the rename: KEEL_* env refs in the README, /keeld build artifact
  ignored, stale antidriftd binary removed.

Include the design + implementation plan this refactor was built from under
docs/superpowers/{specs,plans}/2026-06-04-controller-refactor*.md.

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

internal/evidence/context.go

@@ -3,7 +3,7 @@ package evidence
 import (
 	"strings"
 
-	"antidrift/internal/domain"
+	"keel/internal/mode/focus/domain"
 )
 
 // MatchesAllowed reports whether a window (class/title) is on-task per ctx.

internal/evidence/context_test.go

@@ -3,7 +3,7 @@ package evidence
 import (
 	"testing"
 
-	"antidrift/internal/domain"
+	"keel/internal/mode/focus/domain"
 )
 
 func TestWindowClassMatchesCaseAndTrim(t *testing.T) {

internal/evidence/evidence_test.go

@@ -8,19 +8,19 @@ import (
 
 func TestScrubTitle(t *testing.T) {
 	cases := []struct{ in, want string }{
-		{"Plain title", "Plain title"},                   // no digits-with-separator: untouched
-		{"Buy 2 eggs", "Buy 2 eggs"},                     // bare integer: untouched (group is mandatory)
-		{"12.5%", ""},                                    // percent decimal: stripped whole
-		{"1:23:45 remaining", "remaining"},               // clock ratio: stripped, space collapsed
-		{"-3.0 delta", "delta"},                          // leading sign + decimal: stripped
-		{"Download 50.5% complete", "Download complete"}, // embedded percent decimal
-		{"⠸ antidrift", "antidrift"},                     // braille spinner frame stripped
-		{"⠼ antidrift", "antidrift"},                     // different frame collapses to same key
+		{"Plain title", "Plain title"},                             // no digits-with-separator: untouched
+		{"Buy 2 eggs", "Buy 2 eggs"},                               // bare integer: untouched (group is mandatory)
+		{"12.5%", ""},                                              // percent decimal: stripped whole
+		{"1:23:45 remaining", "remaining"},                         // clock ratio: stripped, space collapsed
+		{"-3.0 delta", "delta"},                                    // leading sign + decimal: stripped
+		{"Download 50.5% complete", "Download complete"},           // embedded percent decimal
+		{"⠸ antidrift", "antidrift"},                               // braille spinner frame stripped
+		{"⠼ antidrift", "antidrift"},                               // different frame collapses to same key
 		{"✳ Check latest commit date", "Check latest commit date"}, // dingbat-star indicator
 		{"⠂ Check latest commit date", "Check latest commit date"}, // same task, different frame
 		{"✳ ⠼ done", "done"},                                       // multiple glyphs in one title
 		{"C++ build", "C++ build"},                                 // ASCII symbols kept (not all-symbols)
-		{"日本語 window", "日本語 window"},                            // non-ASCII letters preserved
+		{"日本語 window", "日本語 window"},                               // non-ASCII letters preserved
 	}
 	for _, c := range cases {
 		if got := ScrubTitle(c.in); got != c.want {

internal/evidence/windows.go

@@ -6,7 +6,7 @@ import (
 	"context"
 	"time"
 
-	"antidrift/internal/winapi"
+	"keel/internal/winapi"
 )
 
 // pollInterval is how often the Windows sensor samples the foreground window.

internal/evidence/x11.go

@@ -86,4 +86,3 @@ func snapshot(X *xgbutil.XUtil) WindowSnapshot {
 		Health: EvidenceHealth{Available: true},
 	}
 }
-