refactor: one door from a tool to the browser

Four routes coexisted: cdpCall, a raw client.session().call, a session
held in a local and called directly, and client.evaluateJs — and five
files mixed two or three of them. The CdpError-to-ToolErr mapping was
hand-copied at nine sites, plus a private copy in isolated-tab.ts.

domains/cdp-call.ts now owns all of it: cdpErrToToolErr, cdpCall,
cdpCallOnTarget, cdpCallBrowser, evalJs. Every other file under
src/domains goes through them, which also removes a pile of
`if (!r.success) return err({ kind: "cdp_error", ... })` boilerplate in
favour of returning the failed Result as-is.

Two scanner rules keep it that way, scoped to src/domains/ so the layer
that legitimately owns the session — cdp/ and client.ts — is unaffected.
Scoping is new to the rule model; without it the rules fired on the
transport itself.

One deliberate behaviour change: a CDP timeout now surfaces as
kind "timeout" rather than "cdp_error". isolated-tab.ts already did this
and the other 13 sites flattened it; the shared mapper uses the honest
label rather than preserving the mislabel.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/src/domains/readpage/read-page.ts b/src/domains/readpage/read-page.ts
index 0a6fadc..9d46c7e 100644
--- a/src/domains/readpage/read-page.ts
+++ b/src/domains/readpage/read-page.ts
@@ -4,6 +4,7 @@ import { parseJson } from "../../schemas/parse";
 import { type Result, err, ok } from "../../util/result";
 import { applyTruncation } from "../../util/truncate";
 import { defineBrowserTool, type ToolErr, type ToolOk } from "../../util/tool";
+import { cdpCallBrowser, evalJs } from "../cdp-call";
 import {
   closeIsolatedTab,
   evalInIsolatedTab,
@@ -107,11 +108,11 @@ const readOwnedTab = async (
   if (!client.owns(targetId)) {
     return err({ kind: "invalid_state", message: `Tab ${targetId} is not owned by this session.` });
   }
-  const attached = await client.session().callBrowser("Target.attachToTarget", { targetId, flatten: true });
-  if (!attached.success) return err({ kind: "cdp_error", message: attached.error.message });
+  const attached = await cdpCallBrowser(client, "Target.attachToTarget", { targetId, flatten: true });
+  if (!attached.success) return attached;
   const sessionId = attached.data.sessionId;
-  const captured = await client.evaluateJs(buildPageCaptureExpr(), sessionId);
-  if (!captured.success) return err({ kind: "cdp_error", message: captured.error.message });
+  const captured = await evalJs(client, buildPageCaptureExpr(), sessionId);
+  if (!captured.success) return captured;
   return captureToResult(captured.data);
 };