Add debug log for 404 in resolveTarget, clarify Test 9b expectations

During production testing, deleted content was silently handled by
resolveTarget returning undefined (correct behavior). Added debug
logging for the 404 case to match the existing deleted-state logging.
Updated README to document the actual flow: silent detection, no
prompt for stale target, falls through to new publish.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: cderv

src/publish/posit-connect-cloud/posit-connect-cloud.ts

@@ -307,6 +307,9 @@ async function resolveTarget(
     };
   } catch (err) {
     if (err instanceof ApiError && err.status === 404) {
+      publishDebug(
+        `Content ${target.id} not found (404), treating as not found`,
+      );
       return undefined;
     }
     throw err;

tests/docs/manual/publish-connect-cloud/README.md

@@ -292,9 +292,11 @@ unset POSIT_CONNECT_CLOUD_ACCESS_TOKEN
 ./package/dist/bin/quarto.cmd publish posit-connect-cloud tests/docs/manual/publish-connect-cloud/single-doc/document.qmd
 ```
 
-- [ ] Detects content is gone (deleted or 404)
-- [ ] Prompts as new publish (or creates new content)
+- [ ] Silently detects content is gone via `resolveTarget` (debug log: "not found" or "deleted")
+- [ ] No "Publish update to:" prompt for the deleted target
+- [ ] Falls through to new publish flow ("Publish with account:" prompt)
 - [ ] Publishes successfully with new content ID
+- [ ] Old stale entry remains in `_publish.yml` (not cleaned up — known limitation)
 
 ### 9c: --no-render Flag