FN-6002: fix raw rgba CSS token violations

Replace raw RGBA styling in scoped dashboard CSS with theme-token-backed values.

- update PullRequestView.css state, banner, error, and disagreement styles to use CSS variables with existing rgba fallbacks
- replace SessionTerminal tooltip box-shadow with the shared shadow token
- exclude out-of-scope Board.canDropTask.test.tsx changes from the squash merge

Files changed:
 packages/dashboard/app/components/PullRequestView.css | 14 +++++++-------
 packages/dashboard/app/components/SessionTerminal.css |  2 +-
 2 files changed, 8 insertions(+), 8 deletions(-)

Fusion-Task-Id: FN-6002

Fusion-Task-Lineage: 1f0431e1-32e8-4c24-9f02-3d641e8b074f

packages/dashboard/app/components/PullRequestView.css

@@ -62,12 +62,12 @@
 }
 
 .pr-identity-state--failed {
-  background: rgba(229, 83, 75, 0.18);
+  background: var(--pr-failed-bg, rgba(229, 83, 75, 0.18));
   color: var(--danger, #e5534b);
 }
 
 .pr-identity-state--merged {
-  background: rgba(130, 80, 223, 0.18);
+  background: var(--pr-merged-bg, rgba(130, 80, 223, 0.18));
 }
 
 /* placeholders / banners / notices */
@@ -84,15 +84,15 @@
 }
 
 .pr-banner--responding {
-  background: rgba(54, 130, 220, 0.14);
+  background: var(--pr-responding-bg, rgba(54, 130, 220, 0.14));
 }
 
 .pr-notice--unverified {
-  background: rgba(220, 170, 54, 0.14);
+  background: var(--pr-unverified-bg, rgba(220, 170, 54, 0.14));
 }
 
 .pr-error-reason {
-  background: rgba(229, 83, 75, 0.14);
+  background: var(--pr-error-bg, rgba(229, 83, 75, 0.14));
   color: var(--danger, #e5534b);
 }
 
@@ -133,7 +133,7 @@
 }
 
 .pr-action--close {
-  border-color: rgba(229, 83, 75, 0.4);
+  border-color: var(--pr-close-border, rgba(229, 83, 75, 0.4));
 }
 
 .pr-automerge-toggle {
@@ -210,7 +210,7 @@
 
 .pr-thread--agent-disagreement {
   border-left: 3px solid var(--warning, #d29922);
-  background: rgba(210, 153, 34, 0.08);
+  background: var(--pr-disagreement-bg, rgba(210, 153, 34, 0.08));
 }
 
 .pr-thread--pending {

packages/dashboard/app/components/SessionTerminal.css

@@ -67,7 +67,7 @@
   background: var(--card);
   border: 1px solid var(--border);
   border-radius: var(--radius-md);
-  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.25);
+  box-shadow: var(--shadow-md);
 }
 
 .cli-posture-tooltip__title {