ci: upgrade to cargo-rbmt 0.5.3

### .github/actions/setup-rbmt/action.yml
@@ -12,10 +12,8 @@ runs:
       shell: bash
       run: |
         cargo install \
-          --git https://git.rust-bitcoin.org/rust-bitcoin/rust-bitcoin-maintainer-tools \
-          --rev "$(cat rbmt-version)" \
-          cargo-rbmt \
-          --locked
+          --locked \
+          cargo-rbmt@$(grep "^rbmt.version" Cargo.toml | cut -d'"' -f2)
 
     - name: "Install Rust toolchains via cargo-rbmt"
       shell: bash

### .github/workflows/corpus-fuzzing.yml
@@ -76,17 +76,15 @@ jobs:
             rust-bitcoin/fuzz/target
             rust-bitcoin/target
           # cached cargo-rbmt binary goes stale when it is bumped.
-          key: fuzz-${{ hashFiles('rust-bitcoin/**/Cargo.toml', 'rust-bitcoin/rbmt-version') }}
+          key: fuzz-${{ hashFiles('rust-bitcoin/**/Cargo.toml') }}
           # On cache miss this loads the latest cache and avoids a rebuild from scratch.
           restore-keys: fuzz-
       - name: Install cargo-rbmt
         working-directory: rust-bitcoin
         run: |
           cargo install \
-            --git https://git.rust-bitcoin.org/rust-bitcoin/rust-bitcoin-maintainer-tools \
-            --rev "$(cat rbmt-version)" \
-            cargo-rbmt \
-            --locked
+            --locked \
+            cargo-rbmt@$(grep "^rbmt.version" Cargo.toml | cut -d'"' -f2)
       - name: Install nightly toolchain
         working-directory: rust-bitcoin
         run: rustup toolchain install "$(cargo rbmt toolchains --nightly)" --profile minimal --no-self-update

### .github/workflows/cron-monthly-update-rbmt.yml
@@ -21,15 +21,14 @@ jobs:
           git clone --filter=blob:none --no-checkout \
             https://github.com/rust-bitcoin/rust-bitcoin-maintainer-tools.git /tmp/rbmt
           LATEST_TAG=$(git -C /tmp/rbmt tag --sort=-version:refname | grep '^cargo-rbmt-' | head -1)
-          LATEST_HASH=$(git -C /tmp/rbmt rev-parse "${LATEST_TAG}^{}")
-          CURRENT_HASH=$(cat rbmt-version)
-          if [ -n "${LATEST_HASH}" ] && [ "${LATEST_HASH}" != "${CURRENT_HASH}" ]; then
-            echo "${LATEST_HASH}" > rbmt-version
-            echo "rbmt_hash=${LATEST_HASH}" >> "${GITHUB_ENV}"
-            echo "rbmt_semver=${LATEST_TAG#cargo-rbmt-}" >> "${GITHUB_ENV}"
+          LATEST_VERSION=${LATEST_TAG#cargo-rbmt-}
+          CURRENT_VERSION=$(grep "^rbmt.version" Cargo.toml | cut -d'"' -f2)
+          if [ -n "${LATEST_VERSION}" ] && [ "${LATEST_VERSION}" != "${CURRENT_VERSION}" ]; then
+            sed -i "s/^rbmt.version = \"${CURRENT_VERSION}\"/rbmt.version = \"${LATEST_VERSION}\"/" Cargo.toml
+            echo "rbmt_semver=${LATEST_VERSION}" >> "${GITHUB_ENV}"
             echo "changes_made=true" >> "${GITHUB_ENV}"
           else
-            echo "rbmt-version is already at the latest release. Not opening any PR."
+            echo "rbmt version is already at the latest release. Not opening any PR."
             echo "changes_made=false" >> "${GITHUB_ENV}"
           fi
       - name: Create Pull Request
@@ -41,6 +40,6 @@ jobs:
           committer: Update RBMT Bot <bot@example.com>
           title: Automated update to cargo-rbmt (to ${{ env.rbmt_semver }})
           body: |
-            Automated update to rbmt-version by [create-pull-request](https://github.com/peter-evans/create-pull-request) GitHub action
+            Automated update to Cargo.toml workspace metadata by [create-pull-request](https://github.com/peter-evans/create-pull-request) GitHub action
           commit-message: Automated update to cargo-rbmt-${{ env.rbmt_semver }}
           branch: create-pull-request/auto-rbmt-update

### .github/workflows/cron-weekly-update-nightly.yml
@@ -21,8 +21,7 @@ jobs:
         with:
           ref: ${{ matrix.branch }}
           persist-credentials: false
-      - name: Install cargo-rbmt
-        run: cargo install --git https://github.com/rust-bitcoin/rust-bitcoin-maintainer-tools.git --rev $(cat rbmt-version) cargo-rbmt
+      - uses: ./.github/actions/setup-rbmt
       - name: Update nightly toolchain in Cargo.toml
         run: |
           cargo rbmt toolchains --update-nightly

### .github/workflows/cron-weekly-update-stable.yml
@@ -20,8 +20,7 @@ jobs:
         with:
           ref: ${{ matrix.branch }}
           persist-credentials: false
-      - name: Install cargo-rbmt
-        run: cargo install --git https://github.com/rust-bitcoin/rust-bitcoin-maintainer-tools.git --rev $(cat rbmt-version) cargo-rbmt
+      - uses: ./.github/actions/setup-rbmt
       - name: Update stable toolchain in Cargo.toml
         run: |
           cargo rbmt toolchains --update-stable

### .github/workflows/rust.yml
@@ -37,7 +37,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        task: [api, lint, docs, docsrs]
+        task: [lint, docs]
     steps:
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
@@ -46,6 +46,19 @@ jobs:
       - name: "Run ${{ matrix.task }}"
         run: cargo rbmt ${{ matrix.task }}
 
+  Generate-API:
+    runs-on: ubuntu-24.04
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+          fetch-depth: 0 # History required for API diff.
+      - uses: ./.github/actions/setup-rbmt
+      - name: "Run API check"
+        run: cargo rbmt api --baseline ${{ github.event.pull_request.base.sha || github.event.before }}
+
   Bench:
     runs-on: ubuntu-24.04
     permissions:

### Cargo.toml
@@ -3,9 +3,10 @@ members = ["addresses", "base58", "bip158", "bitcoin", "chacha20_poly1305", "con
 exclude = ["benches"]
 resolver = "2"
 
-[workspace.metadata.rbmt.toolchains]
-nightly = "nightly-2026-07-02"
-stable = "1.97.1"
+[workspace.metadata]
+rbmt.version = "0.5.3"
+rbmt.toolchains.nightly = "nightly-2026-07-02"
+rbmt.toolchains.stable = "1.97.1"
 
 [workspace.lints.rust]
 unexpected_cfgs = { level = "deny", check-cfg = ['cfg(bench)', 'cfg(chacha20_poly1305_fuzz)', 'cfg(fuzzing)', 'cfg(hashes_fuzz)', 'cfg(kani)'] }

### contrib/ensure-maintainer-tools.sh
@@ -1,16 +0,0 @@
-#!/usr/bin/env bash
-#
-# Ensure maintainer tools are available locally for CI task execution.
-
-set -euo pipefail
-
-REPO_DIR=$(git rev-parse --show-toplevel)
-
-cd "$REPO_DIR"
-
-if ! command -v cargo-rbmt >/dev/null 2>&1; then
-    echo "Error: cargo-rbmt is required for maintainer tools but not found in PATH" >&2
-    echo "Please ensure it's available in your environment or install cargo-rbmt using:" >&2
-    echo "cargo +stable install --git https://github.com/rust-bitcoin/rust-bitcoin-maintainer-tools.git --rev \"$(cat "$REPO_DIR/rbmt-version")\" cargo-rbmt --locked" >&2
-    exit 1
-fi

### justfile
@@ -1,30 +1,34 @@
 alias ulf := update-lock-files
 
+export RBMT_LOG_LEVEL := env("RBMT_LOG_LEVEL", "progress")
+
 _default:
   @just --list
 
 # Install necessary dev tools on system.
 [group('system')]
-tools:
-  @{{justfile_directory()}}/contrib/ensure-maintainer-tools.sh
-
-# Install workspace toolchains.
-[group('system')]
-@toolchains: tools
-  RBMT_LOG_LEVEL=quiet cargo rbmt toolchains > /dev/null
+@tools:
+  cargo install --quiet --locked cargo-rbmt@$(grep "^rbmt.version" {{justfile_directory()}}/Cargo.toml | cut -d'"' -f2)
 
 # Setup rbmt and run with given args.
-@rbmt *args: toolchains
-  RBMT_LOG_LEVEL=quiet cargo rbmt {{args}}
+@rbmt *args: tools
+  cargo rbmt {{args}}
 
 # Format workspace.
-@fmt: (rbmt "fmt")
+fmt: (rbmt "fmt")
 
-# Check for API changes.
-check-api: (rbmt "api")
+# Lint everything.
+lint: (rbmt "lint")
+
+# Test everything.
+test: (rbmt "test")
 
 # Update the recent and minimal lock files.
-@update-lock-files: (rbmt "lock")
+update-lock-files: (rbmt "lock")
+
+# Check error re-exports.
+check-error-reexports:
+  {{justfile_directory()}}/contrib/check-error-reexports.sh
 
 # Query the current API.
 [group('scripts')]

### rbmt-version
@@ -1 +0,0 @@
-0361e3b0147b799d6e3965bedec8f4be68b21361