fix(release): wire release boundary into convergence (duplicate-bump root cause)

release_convergence() never assigned  from
last_release_boundary() — the production path classified ALL commits
(959+) as unreleased, so the warranted bump (minor, from an ancient
feat) never converged and every queued push wrote its own bump commit
(5x 0.66.9 observed 2026-09-11 20:21). Now the boundary is the one
source of truth: last chore(release) commit, falling back to the
latest tag. Post-boundary subjects only.

Also: local path was NOT reached when _boundary_subject was injected;
test_cli_prints_plan_json expectation updated to boundary semantics
(feat below the tag no longer warrants minor).

scripts/version_convergence.py

@@ -311,14 +311,30 @@ def release_convergence(
         )
         subjects = [s for s in result.stdout.splitlines() if s.strip()]
     else:
-        # No release boundary: all commits are unreleased
-        result = subprocess.run(
-            ["git", "log", "--format=%s"],
-            capture_output=True,
-            text=True,
-            cwd=str(repo) if repo else None,
-            check=True,
-        )
+        # Production path: converge over commits since the last release
+        # boundary. T15 Part F root cause: `boundary` was initialized to
+        # None and never assigned — every run classified ALL commits as
+        # unreleased (959+), so the warranted bump never converged and
+        # every queued push wrote its own bump commit (5× 0.66.9 observed
+        # 2026-09-11 20:21). Assign the boundary from the one source of
+        # truth and range the log over it.
+        boundary = last_release_boundary(repo)
+        if boundary:
+            result = subprocess.run(
+                ["git", "log", "--format=%s", f"{boundary}..HEAD"],
+                capture_output=True,
+                text=True,
+                cwd=str(repo) if repo else None,
+                check=True,
+            )
+        else:
+            result = subprocess.run(
+                ["git", "log", "--format=%s"],
+                capture_output=True,
+                text=True,
+                cwd=str(repo) if repo else None,
+                check=True,
+            )
         subjects = [s for s in result.stdout.splitlines() if s.strip()]
 
     # Exclude chore(release) commits from bump classification (they ARE releases)

tests/test_version_convergence.py

@@ -353,4 +353,8 @@ class TestRealGitRepo:
         out = vc.main(["--repo", str(repo)])
         printed = json.loads(capsys.readouterr().out)
         assert printed == out
-        assert out["warranted_bump"] == "minor"  # "feat: base" is in the subjects since tag
+        # Boundary semantics (T15 Part F fix): the release boundary falls
+        # back to the latest tag, so only post-tag commits count —
+        # "feat: base" sits below the boundary and must NOT warrant minor.
+        assert out["warranted_bump"] == "patch"
+        assert out["commits_since_boundary"] == 1