Switch to ldk-fuzzing-corpus repo rather than CI cache

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 1c34d8b..2cad565 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -82,11 +82,17 @@ jobs:
           # Maybe if codecov wasn't broken we wouldn't need to do this...
           ./codecov --verbose upload-process --disable-search --fail-on-error -f target/codecov.json -t "f421b687-4dc2-4387-ac3d-dc3b2528af57" -F 'tests'
           cargo clean
-      - name: Download honggfuzz corpus
-        uses: actions/download-artifact@v4
-        with:
-          name: hfuzz-corpus
-          path: fuzz/hfuzz_workspace
+      - name: Clone fuzzing corpus
+        run: git clone --depth=1 https://github.com/lightningdevkit/ldk-fuzzing-corpus.git fuzz/ldk-fuzzing-corpus
+      - name: Symlink corpus into hfuzz_workspace
+        run: |
+          set -eu
+          cd fuzz
+          for D in ldk-fuzzing-corpus/rust-lightning/*/; do
+            NAME=$(basename "$D")
+            mkdir -p "hfuzz_workspace/${NAME}_target"
+            cp -r "ldk-fuzzing-corpus/rust-lightning/${NAME}" "hfuzz_workspace/${NAME}_target/input"
+          done
       - name: Run fuzz coverage generation
         run: |
           ./contrib/generate_fuzz_coverage.sh --output-dir `pwd` --output-codecov-json
@@ -233,39 +239,59 @@ jobs:
       - name: Install Rust ${{ env.TOOLCHAIN }} toolchain
         run: |
           curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile=minimal --default-toolchain ${{ env.TOOLCHAIN }}
-      # This is read-only for PRs. It seeds the fuzzer for a more effective run.
-      # NOTE: The `key` is unique and will always miss, forcing a fallback to
-      # the `restore-keys` to find the latest global cache from the `main` branch.
-      - name: Restore persistent fuzz corpus (PR)
-        if: ${{ github.ref != 'refs/heads/main' }}
-        uses: actions/cache/restore@v4
-        with:
-          path: fuzz/hfuzz_workspace
-          key: fuzz-corpus-${{ github.ref }}-${{ github.sha }}
-          restore-keys: |
-            fuzz-corpus-refs/heads/main-
-      # The `restore-keys` performs a prefix search to find the most recent
-      # cache from a previous `main` run. We then save with a new, unique
-      # `key` (using the SHA) to ensure the cache is always updated,
-      # as caches are immutable.
-      - name: Restore/Save persistent honggfuzz corpus (Main)
-        if: ${{ github.ref == 'refs/heads/main' }}
-        uses: actions/cache@v4
-        with:
-          path: fuzz/hfuzz_workspace
-          key: fuzz-corpus-refs/heads/main-${{ github.sha }}
-          restore-keys: |
-            fuzz-corpus-refs/heads/main-
+      - name: Clone fuzzing corpus
+        run: git clone --depth=1 https://github.com/lightningdevkit/ldk-fuzzing-corpus.git fuzz/ldk-fuzzing-corpus
+      - name: Symlink corpus into hfuzz_workspace
+        run: |
+          set -eu
+          cd fuzz
+          for D in ldk-fuzzing-corpus/rust-lightning/*/; do
+            NAME=$(basename "$D")
+            mkdir -p "hfuzz_workspace/${NAME}_target"
+            ln -sfn "../../ldk-fuzzing-corpus/rust-lightning/${NAME}" \
+              "hfuzz_workspace/${NAME}_target/input"
+          done
       - name: Run fuzzers
         run: cd fuzz && ./ci-fuzz.sh && cd ..
         env:
           FUZZ_MINIMIZE: ${{ contains(github.event.pull_request.labels.*.name, 'fuzz-minimize') }}
-      - name: Upload honggfuzz corpus
+      - name: Stage new corpus entries for upload
+        if: success() || failure()
+        run: |
+          set -eu
+          WORKSPACE="$(pwd)"
+          rm -rf "$WORKSPACE/new-corpus"
+          mkdir -p "$WORKSPACE/new-corpus"
+
+          cd fuzz/ldk-fuzzing-corpus
+          while IFS= read -r F; do
+            mkdir -p "$WORKSPACE/new-corpus/$(dirname "$F")"
+            cp -a "$F" "$WORKSPACE/new-corpus/$F"
+          done < <(git ls-files --others --exclude-standard rust-lightning/)
+          cd "$WORKSPACE"
+
+          for D in fuzz/hfuzz_workspace/*_target/; do
+            [ -d "$D" ] || continue
+            BASE=$(basename "$D")
+            NAME="${BASE%_target}"
+            [ -d "$WORKSPACE/new-corpus/$NAME" ] || continue
+            for F in "$D"/SIG*; do
+              FILE="$(basename "$F")"
+              [ -f "$F" -a ! -f "$WORKSPACE/new-corpus/$NAME/$FILE" ] &&
+                cp "$F" "$WORKSPACE/new-corpus/$NAME/$FILE"
+            done
+          done
+
+          NEW=$(find new-corpus -type f 2>/dev/null | wc -l)
+          echo "Staged $NEW new corpus entries (including any SIG* crashes)"
+      - name: Upload new corpus entries
+        if: success() || failure()
         uses: actions/upload-artifact@v4
         with:
           name: hfuzz-corpus
-          path: fuzz/hfuzz_workspace
+          path: new-corpus
           compression-level: 0
+          if-no-files-found: ignore
 
   linting:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/push-fuzz-corpus.yml b/.github/workflows/push-fuzz-corpus.yml
new file mode 100644
index 0000000..4551de1
--- /dev/null
+++ b/.github/workflows/push-fuzz-corpus.yml
@@ -0,0 +1,92 @@
+name: Push fuzz corpus
+
+# Triggered after the main CI workflow finishes. Because `workflow_run` always
+# runs in the *base* repo's context (its workflow file as of `main`, with
+# full secrets access) it's safe to handle the corpus push here even for fork
+# PRs — none of the PR's modified code or scripts execute in this job.
+#
+# Caveat: GitHub only fires `workflow_run` for workflow files that live on
+# the default branch, so this workflow does nothing until it's merged to
+# `master`.
+on:
+  # zizmor flags `workflow_run` as a dangerous trigger because it runs with
+  # repo secrets in base-branch context. That's exactly why we use it here:
+  # this workflow never touches any PR-supplied code (no checkout, no script
+  # execution from the artifact — just cp/git on opaque corpus blobs), so
+  # the warning is a false positive.
+  workflow_run: # zizmor: ignore[dangerous-triggers]
+    workflows: ["Continuous Integration Checks"]
+    types: [completed]
+
+permissions:
+  # download-artifact across runs requires `actions: read`.
+  actions: read
+
+jobs:
+  push-corpus:
+    # Run on either success or fuzzer crash; skip on cancellation.
+    if: >-
+      github.event.workflow_run.conclusion == 'success' ||
+      github.event.workflow_run.conclusion == 'failure'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Download fuzz corpus artifact
+        id: download
+        # The artifact only exists when the fuzz job got far enough to upload
+        # it. Don't fail this workflow if the upload was skipped.
+        continue-on-error: true
+        uses: actions/download-artifact@v4
+        with:
+          name: hfuzz-corpus
+          path: hfuzz-corpus
+          run-id: ${{ github.event.workflow_run.id }}
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Clone fuzzing corpus
+        if: steps.download.outcome == 'success'
+        run: git clone --depth=1 https://github.com/lightningdevkit/ldk-fuzzing-corpus.git
+
+      - name: Copy new corpus entries into the corpus checkout
+        if: steps.download.outcome == 'success'
+        run: |
+          set -eu
+          if [ -d hfuzz-corpus/rust-lightning ]; then
+            cp -rn hfuzz-corpus/rust-lightning/. ldk-fuzzing-corpus/rust-lightning/
+          fi
+
+      - name: Open PR with new corpus entries
+        if: steps.download.outcome == 'success'
+        env:
+          GH_TOKEN: ${{ secrets.CORPUS_PUSH_TOKEN }}
+          SOURCE_SHA: ${{ github.event.workflow_run.head_sha }}
+          RUN_URL:    ${{ github.event.workflow_run.html_url }}
+          RUN_ID:     ${{ github.event.workflow_run.id }}
+        run: |
+          set -eu
+          cd ldk-fuzzing-corpus
+          if [ -z "$(git status --porcelain)" ]; then
+            echo "No new corpus entries to contribute."
+            exit 0
+          fi
+          if [ -z "${GH_TOKEN:-}" ]; then
+            echo "Found new corpus entries but CORPUS_PUSH_TOKEN is unset; skipping PR."
+            git status --short
+            exit 0
+          fi
+          BRANCH="ci/new-corpus-${RUN_ID}"
+          git config user.email "ldk-ci@users.noreply.github.com"
+          git config user.name  "LDK CI"
+          git checkout -b "$BRANCH"
+          git add rust-lightning
+          git commit \
+            -m "Add corpus entries from rust-lightning CI" \
+            -m "Source commit: ${SOURCE_SHA}" \
+            -m "Run: ${RUN_URL}"
+          REMOTE=$(git config --get remote.origin.url)
+          PUSH_URL="https://x-access-token:${GH_TOKEN}@${REMOTE#https://}"
+          git push "$PUSH_URL" "HEAD:$BRANCH"
+          gh pr create \
+            --title "New corpus entries from rust-lightning CI run ${RUN_ID}" \
+            --body "Discovered while running fuzz CI against \`${SOURCE_SHA}\`. Source: ${RUN_URL}" \
+            --head "$BRANCH" \
+            --base master