feat: add evidence search and stabilize pdf previews

- add document evidence parsing/search/open routes, Hermes tool wiring, local index settings/status, and the document-evidence skill plus design notes
- fix PDF resource tabs by rendering PDFs inline with pdf.js canvases instead of iframe preview pages, release PDF documents on close, and document the fourth-PDF stall bug
- keep PDF preview at 2x rendering while removing the previous lazy-load/placeholder direction, and make dev:hot bind loopback defaults externally reachable

Verification:
- node --check rust/crates/mnote-web/browser/document-resource-tab-runtime.js
- node scripts/task-dev-hot-plan-test.js
- cargo test -p mnote-web --manifest-path rust/Cargo.toml pdf_preview_page_does_not_render_visible_toolbar
- cargo test -p mnote-web --manifest-path rust/Cargo.toml document_shell_returns_page_aggregate_snapshot
- cargo build -p mnote-web --manifest-path rust/Cargo.toml
- browser smoke: sequentially opened the four tea_seed_oil_cosmetic PDFs; fourth PDF rendered 15/15 canvases, iframeCount=0, browser errors=0

rust/crates/mnote-web/src/hermes_tools/skill.rs

@@ -31,6 +31,22 @@ const SKILLS: &[MnoteSkill] = &[
         ],
         content: include_str!("../../../../../skills/mnote-current-page/SKILL.md"),
     },
+    MnoteSkill {
+        id: "mnote-document-evidence",
+        title: "MNote document evidence",
+        description: "Search local documents and resources with clickable evidence locators.",
+        agent_ids: &["hermes", "reasonix"],
+        read_only: true,
+        requires_context_refs: &["folder"],
+        tool_names: &[
+            "mnote.context.snapshot",
+            "mnote.context.resolve_target",
+            "mnote.evidence.search",
+            "mnote.evidence.read",
+            "mnote.evidence.open",
+        ],
+        content: include_str!("../../../../../skills/mnote-document-evidence/SKILL.md"),
+    },
     MnoteSkill {
         id: "mnote-local-file",
         title: "MNote local file editing",
@@ -279,6 +295,21 @@ mod tests {
             .any(|name| name == "mnote.mindmap.create_from_outline"));
     }
 
+    #[test]
+    fn skill_registry_exposes_document_evidence_skill_to_agents() {
+        let hermes_skills = skill_summaries_for_agent(Some("hermes"));
+        let skill = hermes_skills
+            .iter()
+            .find(|skill| skill["id"] == "mnote-document-evidence")
+            .expect("hermes should see document evidence skill");
+        assert_eq!(skill["readOnly"], true);
+        assert!(skill["toolNames"]
+            .as_array()
+            .expect("tool names")
+            .iter()
+            .any(|name| name == "mnote.evidence.search"));
+    }
+
     #[tokio::test]
     async fn skill_read_returns_mindmap_skill_content() {
         let context = RequestContext::from_http_parts(