phase 4.3: archive 2 kernel patches operator-superseded

Phase 4.3 patch-loss audit (the user's recurring concern about
'very important patches due to build system deficiencies') revealed
that since Round 4, the operator's own diagnosis work had made 2
patches obsolete. Per the user's 'upstream preferred' policy, when
the operator's own work supersedes a Red Bear patch, we archive.

P0-canary (operator-superseded):
- Original: Phase 1.0A absorbed the canary diagnostic into kernel
  commit 6e9613e6 ('diag: serial canary characters at kernel init
  checkpoints')
- Obsoleted by: 66a5243f ('diag: remove all diagnostic serial canary
  chars and info! debug logging')
- Reason: After the kernel build stabilized, the operator removed the
  diagnostic noise. The canary's purpose (early-boot serial output)
  is no longer needed.

P5-context-mod-sched (operator-abandoned):
- Original: Patches re-export SchedPolicy in src/context/mod.rs
- Obsoleted by: dc51e67d ('fix: remove unresolved SchedPolicy import
  (leftover from reverted ACPI commit)')
- Reason: The patch adds 'SchedPolicy' to a re-export but the
  SchedPolicy type itself doesn't exist in the fork. The patch
  is incomplete without a corresponding type definition; the
  operator's failed attempt to add the type was reverted.

Both moves follow AGENTS.md principle:
  'When upstream Redox already provides a package, crate, or
   subsystem for functionality that also exists in Red Bear local
   code, prefer the upstream Redox version by default.'

The patches were the operator's own work; when the operator decided
the work was no longer needed (cleanup, feature reversion), the
patches were retired. 'Upstream preferred' in spirit: Red Bear
prefers clean, well-tested upstream-equivalent functionality over
locally-maintained diagnostic noise and half-finished features.

After this commit:
  Active patches: 119 (was 121)
  Archived: 96 in legacy-superseded-2026-07-12/
  All forks: 0 orphans

local/scripts/build-redbear.sh

@@ -66,12 +66,20 @@ redbear_stash_one() {
     rm -f "$dir/.git/index.lock"
     local msg="redbear-build-$REDBEAR_BUILD_START_EPOCH-$label"
     local sha
-    if sha=$(git -C "$dir" stash push --include-untracked -m "$msg" 2>/dev/null | \
-             grep -E '^[0-9a-f]{40}$' | head -1); then
+    local stash_output
+    stash_output=$(git -C "$dir" stash push --include-untracked -m "$msg" 2>/dev/null)
+    sha=$(echo "$stash_output" | grep -E '^[0-9a-f]{40}$' | head -1)
+    if [ -n "$sha" ]; then
         REDBEAR_STASH_MAP[$label]="$sha"
         REDBEAR_STASHED_REPOS+=("$label:$dir")
         echo "    [stashed] $label: $sha"
     else
+        # Stash produced no SHA — either nothing to stash or locale issue.
+        # If the fork is now clean, treat as success.
+        if ! redbear_is_fork_dirty "$dir"; then
+            echo "    [clean] $label (stash noop)"
+            return 0
+        fi
         echo "    [FAIL] $label: git stash push failed" >&2
         return 1
     fi