feat(opencode): state whether the code mode tool list is complete or partial

The preview now reports its own comprehensiveness so the model knows when it
has the whole catalog vs. when it must search:

- Overall: "This is the COMPLETE list ..." when every tool fits the budget,
  else "This is a PARTIAL list — X of Y tools are shown ...".
- Per namespace: a fully-shown server reads `- github (2 tools)`; a truncated
  one is annotated `- alpha (70 tools, 31 shown)` or `- zeta (1 tool, none shown)`.

When complete, the model isn't pushed toward needless $rune.search calls; when
partial, exactly what's missing is unambiguous.

packages/opencode/test/session/code-mode.test.ts

@@ -82,7 +82,8 @@ describe("code mode execute", () => {
 
     expect(description).toContain("tools.$rune.search(query")
     expect(description).toContain("tools.$rune.describe(path)")
-    // Every namespace is always listed, with counts.
+    // Small catalog: the list is comprehensive and says so, with clean counts.
+    expect(description).toContain("This is the COMPLETE list")
     expect(description).toContain("- github (2 tools)")
     expect(description).toContain("- linear (1 tool)")
     // Tools are previewed inline as compact, directly-callable input signatures.
@@ -104,10 +105,11 @@ describe("code mode execute", () => {
     const groups = groupByServer(tools, ["alpha", "zeta"])
     const description = describeTools(groups)
 
-    // Every namespace is always present, with counts.
-    expect(description).toContain("- alpha (60 tools)")
-    expect(description).toContain("- zeta (1 tool)")
-    // The preview is budget-capped, so the later namespace's signatures are not all inlined.
+    // The list states it is partial, and every namespace is still present with its total.
+    expect(description).toContain("This is a PARTIAL list")
+    expect(description).toContain("- alpha (60 tools")
+    // The later namespace is fully truncated, and says so.
+    expect(description).toContain("- zeta (1 tool, none shown)")
     expect(description).not.toContain("tools.zeta.only_tool(")
     // Some early signatures are still previewed.
     expect(description).toContain("tools.alpha.op_0(")