feat(stuck): stuck-state pipeline overlay (cad-atlas#11)

Consumes mathias/cad#14's cad-stuck query directly — cad's app/domain
packages are public Go modules, so this reuses the exact tested
classification logic (import, not re-implementation) rather than
duplicating the taxonomy across two repos.

ApplyStuckOverlay (internal/atlas/stuck.go, fixture-tested) maps each
finding's category onto the existing 9-stage pipeline: armed_never_fired to
the human dispatch gate, claimed_never_ran/ceiling_hit/refire_loop/
near_attempt_cap to the one Execute stage (there is no separate Claim
stage), done_not_closed to the loop-back stage. Adds a StuckCount/
AwaitingCount badge per stage plus one Node per finding, linking out to the
underlying issue/comment — read-only, no controls, matching cad#14's own
constraint.

Two visual classes, kept deliberately distinct per the issue's own framing:
a coral 'N stuck' badge (needs intervention) vs a green 'N awaiting' badge
(a functioning control waiting on a human) — done_not_closed can never
render as a bottleneck.

Verified against the live estate: STAGE 05 shows 2 stuck (cobalt-dingo#30
ceiling_hit, cad-atlas#10 near_attempt_cap), STAGE 08 shows 5 awaiting
(cobalt-dingo #3/#7/#12/#16/#19 done_not_closed) — screenshotted via a
koala k3s Playwright job against a live-token server, matching cad#14's own
proven query output exactly.

go.mod: added git.d-ma.be/mathias/cad v0.10.0 (app/domain/adapters-gitearead
only — no mcp-chassis pulled in, that's only imported by cad's own cmd/cad).
Dockerfile: added the same GOPRIVATE/insteadOf fetch config mathias/cad's
own Dockerfile uses, now needed for this new private-module dependency.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

internal/atlas/model.go

@@ -42,7 +42,13 @@ type Stage struct {
 	Generate   string `json:"generate,omitempty"`
 	TransLabel string `json:"trans_label,omitempty"`
 	Trans      string `json:"trans,omitempty"`
-	Nodes      []Node `json:"nodes"`
+	// StuckCount/AwaitingCount are set by ApplyStuckOverlay (cad-atlas#11) on
+	// stages marked `"generate":"stuck-badges"` — the two visual classes the
+	// issue asks for kept as separate counts so a functioning control
+	// (awaiting human) can never be rendered as a bottleneck (stuck).
+	StuckCount    int    `json:"stuck_count,omitempty"`
+	AwaitingCount int    `json:"awaiting_count,omitempty"`
+	Nodes         []Node `json:"nodes"`
 }
 
 // Atlas is the full data model the frontend renders.