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/core-protocol/src/tool.rs

@@ -140,6 +140,39 @@ pub const DOCS_TOOL_READ: ToolSpec = ToolSpec {
     input_schema_json: r#"{"type":"object","required":["documentId"],"properties":{"documentId":{"type":"string"},"maxChars":{"type":"integer","minimum":200,"maximum":20000},"includeContent":{"type":"boolean"}}}"#,
 };
 
+pub const EVIDENCE_TOOL_SEARCH: ToolSpec = ToolSpec {
+    name: "mnote.evidence.search",
+    display_name: "证据搜索",
+    description: "在工作区内搜索可回跳原文的证据块，返回 quote、locator 与 openAction。",
+    toolset_id: "toolset.evidence_read",
+    invocation_kind: InvocationKind::Query,
+    effect: ToolEffect::Read,
+    requires_confirmation: false,
+    input_schema_json: r#"{"type":"object","required":["query","scope"],"properties":{"query":{"type":"string"},"scope":{"type":"object","required":["workspaceId","rootUri"],"properties":{"workspaceId":{"type":"string"},"rootUri":{"type":"string"},"targetDocumentId":{"type":"string"},"includeResources":{"type":"boolean"},"includeOcr":{"type":"boolean"}}},"mode":{"enum":["keyword","tree","hybrid","graph"]},"topK":{"type":"integer","minimum":1,"maximum":30}}}"#,
+};
+
+pub const EVIDENCE_TOOL_READ: ToolSpec = ToolSpec {
+    name: "mnote.evidence.read",
+    display_name: "证据读回",
+    description: "按 EvidenceLocator 读取原文证据及周边上下文，供 AI 回答引用。",
+    toolset_id: "toolset.evidence_read",
+    invocation_kind: InvocationKind::Query,
+    effect: ToolEffect::Read,
+    requires_confirmation: false,
+    input_schema_json: r#"{"type":"object","required":["locator"],"properties":{"locator":{"type":"object"},"context":{"type":"object","properties":{"beforeBlocks":{"type":"integer","minimum":0,"maximum":20},"afterBlocks":{"type":"integer","minimum":0,"maximum":20},"includeSectionSummary":{"type":"boolean"}}}}}"#,
+};
+
+pub const EVIDENCE_TOOL_OPEN: ToolSpec = ToolSpec {
+    name: "mnote.evidence.open",
+    display_name: "证据打开",
+    description: "把 EvidenceLocator 归一化为 MNote 可执行的打开/定位动作。",
+    toolset_id: "toolset.evidence_read",
+    invocation_kind: InvocationKind::Query,
+    effect: ToolEffect::Read,
+    requires_confirmation: false,
+    input_schema_json: r#"{"type":"object","required":["locator"],"properties":{"locator":{"type":"object"}}}"#,
+};
+
 pub const IMAGE_READ_TOOL: ToolSpec = ToolSpec {
     name: "image_read",
     display_name: "读取图片",
@@ -387,6 +420,18 @@ pub const DOCS_TOOLSET_READ: ToolSetSpec = ToolSetSpec {
     tool_names: &["docs_search", "docs_read"],
 };
 
+pub const EVIDENCE_TOOLSET_READ: ToolSetSpec = ToolSetSpec {
+    id: "toolset.evidence_read",
+    display_name: "证据读取",
+    description: "搜索、读回和打开可定位原文证据的只读工具集合。",
+    write_toolset: false,
+    tool_names: &[
+        "mnote.evidence.search",
+        "mnote.evidence.read",
+        "mnote.evidence.open",
+    ],
+};
+
 pub const READONLY_TOOLSET: ToolSetSpec = ToolSetSpec {
     id: "toolset.readonly",
     display_name: "只读工具",
@@ -481,6 +526,7 @@ pub const DOC_TOOL_REGISTRY: ToolRegistry = ToolRegistry::new(
         MEDIA_TOOLSET,
         SLASH_TOOLSET_WRITE,
         DOCS_TOOLSET_READ,
+        EVIDENCE_TOOLSET_READ,
         DOC_TOOLSET_READ,
         DOC_TOOLSET_WRITE,
         MINDMAP_TOOLSET_READ,
@@ -495,6 +541,9 @@ pub const DOC_TOOL_REGISTRY: ToolRegistry = ToolRegistry::new(
         DOC_TOOL_FIND,
         DOCS_TOOL_SEARCH,
         DOCS_TOOL_READ,
+        EVIDENCE_TOOL_SEARCH,
+        EVIDENCE_TOOL_READ,
+        EVIDENCE_TOOL_OPEN,
         IMAGE_READ_TOOL,
         DOC_TOOL_INSERT_BLOCKS,
         DOC_TOOL_REPLACE_RANGE,