feat: add repo_commits_total to the AI security-context schema

internal/schemavalidators/internal_schemas/aisecuritycontext/ai-security-context-0.1.schema.json

@@ -429,6 +429,11 @@
           "minimum": 0,
           "description": "How many survivors the context holds at the covered window."
         },
+        "repo_commits_total": {
+          "type": "integer",
+          "minimum": 0,
+          "description": "Total number of commits reachable from the scanned revision (git rev-list --count of the target SHA). The denominator a consumer needs to render scan progress as \"N of M commits\" or a percentage. OPTIONAL: omitted when unknown — a shallow clone (whose count would be truncated) or an artifact produced before this field existed. The managed flow mirror-clones full history, so it is populated there. A snapshot of repository size, not a funnel counter, so it is not part of the reconciles invariant."
+        },
         "pending_survivors": {
           "type": "integer",
           "minimum": 0,

pkg/attestation/crafter/materials/aisecuritycontext/aisecuritycontext.go

@@ -117,6 +117,12 @@ type ScanStats struct {
 	// SurvivorsTotal is how many survivors the context holds at the covered
 	// window.
 	SurvivorsTotal int `json:"survivors_total,omitempty"`
+	// RepoCommitsTotal is the total number of commits reachable from the scanned
+	// revision — the denominator a consumer renders scan progress against
+	// ("N of M commits"). A snapshot pinned to the target SHA, not a funnel counter,
+	// so it is outside the reconciles invariant. Omitted (zero) when unknown: a
+	// shallow clone, or an artifact produced before this field existed.
+	RepoCommitsTotal int `json:"repo_commits_total,omitempty"`
 	// PendingSurvivors is how many survivors still await adjudication: neither in
 	// the frontier, nor a triage hole, nor abandoned after the retry cap. Zero
 	// alongside AdjudicationComplete is the drained queue.

pkg/attestation/crafter/materials/testdata/ai-security-context.json

@@ -53,7 +53,8 @@
           "sha": "d514564a92bf4f472b0ac21cbac794a9494346f4",
           "reason": "diff too large (2065160 bytes)"
         }
-      ]
+      ],
+      "repo_commits_total": 149841
     },
     "class_counts": {
       "access_control": 1,