feat: add git-setup-remotes and git-sign-push CLIs

Ship the two maintainer workflow helpers as installable Python CLIs so
any fork-based OSS project can reuse them without vendoring shell
scripts:

  * git-setup-remotes configures origin/fork/main-tracking/pushDefault
    for a fork-based clone. URLs are parameterized (--canonical / --fork
    or CANONICAL_URL / FORK_URL) so the same binary bootstraps any
    maintainer's repo. Idempotent.
  * git-sign-push GPG-signs every unpushed commit on the current branch
    and pushes, resolving the target remote from remote.pushDefault
    (falling back to origin) for branches without upstream.

Both refuse to run when CLAUDE_CODE/CLAUDECODE is set, since the Claude
sandbox blocks .git/config writes and access to ~/.gnupg: failing fast
beats failing late.

Other additions:
  * Makefile: install / install-dev / test / lint / clean targets.
  * .github/workflows/test.yml: pytest + ruff matrix for py 3.10/11/12.
  * MIRRORS: github, git.veen.world:2201, code.infinito.nexus:2201, pypi.
  * LICENSE switched to MIT; README records the extraction origin
    (s.infinito.nexus/code) and adds author + license sections.
  * Tests cover sandbox-refusal guards and the fork-URL resolution
    preference order (CLI arg > env var > existing fork remote > origin
    when not canonical).

.github/FUNDING.yml

@@ -0,0 +1,7 @@
+github: kevinveenbirkenbach
+
+patreon: kevinveenbirkenbach
+
+buy_me_a_coffee: kevinveenbirkenbach
+
+custom: https://s.veen.world/paypaldonate

.github/workflows/test.yml

@@ -0,0 +1,37 @@
+name: tests
+
+on:
+  push:
+    branches: ["**"]
+  pull_request:
+    branches: ["**"]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    name: test (python ${{ matrix.python-version }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.10", "3.11", "3.12"]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+          cache: pip
+
+      - name: Install with dev extras
+        run: make install-dev
+
+      - name: Lint
+        run: make lint
+
+      - name: Run tests
+        run: make test