harden(search_code): defensive arg coercion, per-line truncation, rerun-safe pkg

Address findings from a second independent (Gemini) review covering the tool
and the packaging:

- Robustness (was: crash): non-string params from a model hallucination (e.g.
  include_ext: ["ts","go"]) threw 'x.trim is not a function' and killed the
  tool call. Add an asString() coercion for all string params (query, path,
  include_ext, exclude_pattern, only); non-strings now no-op or return the
  graceful 'query is required' error.
- Output bound: cap each rendered snippet line at 500 chars (MAX_LINE_CHARS,
  mirrors read-file.ts) so a matched minified/generated line can't bloat the
  payload. (Total output is already bounded by the universal truncator.)
- packaging/PKGBUILD: make the cs clone rerun-safe (rm -rf before clone) so
  makepkg -e / repeat runs don't abort on 'destination path already exists';
  add conflicts=('cs') to the code-search package for a clean pacman error vs.
  the unrelated AUR 'cs' that also owns /usr/bin/cs (no provides — different
  program).

Not changed (verified): path containment, the -- flag-injection guard, and the
deterministic pinned Docker build were all confirmed solid by the review.

Tests: +2 (wrong-type params don't crash; long-line truncation). Full suite
605 pass, biome + tsc green.

1 files changed, 48 insertions, 0 deletions

diff --git a/packages/core/tests/tools/search-code.test.ts b/packages/core/tests/tools/search-code.test.ts
index d43158a..00eee4c 100644
--- a/packages/core/tests/tools/search-code.test.ts
+++ b/packages/core/tests/tools/search-code.test.ts
@@ -63,6 +63,28 @@ describe("search_code tool", () => {
 		expect(out).toContain("query is required");
 	});
 
+	it("does not crash when params are the wrong type (model hallucination)", async () => {
+		const tool = createSearchCodeTool(workDir);
+		// A non-string query must be rejected gracefully, not throw.
+		const q = await tool.execute({ query: ["a", "b"] as unknown as string });
+		expect(q).toMatch(/^Error:/);
+		expect(q).toContain("query is required");
+		// A non-string include_ext (array) must not throw "x.trim is not a function".
+		const stubDir = await mkdtempP(join(tmpdir(), "dispatch-cs-stub-"));
+		try {
+			process.env.DISPATCH_CS_BIN = writeStub(stubDir, ECHO_ENV_STUB);
+			process.env.CS_STUB_OUTPUT = "null";
+			const out = await tool.execute({
+				query: "x",
+				include_ext: ["ts", "go"] as unknown as string,
+				exclude_pattern: { a: 1 } as unknown as string,
+			});
+			expect(out).toBe("No matches found.");
+		} finally {
+			await rmP(stubDir, { recursive: true, force: true });
+		}
+	});
+
 	it("rejects a path outside the working directory", async () => {
 		const tool = createSearchCodeTool(workDir);
 		const out = await tool.execute({ query: "anything", path: "../../etc" });
@@ -181,6 +203,32 @@ describe("search_code tool", () => {
 		}
 	});
 
+	it("truncates an excessively long snippet line", async () => {
+		const stubDir = await mkdtempP(join(tmpdir(), "dispatch-cs-stub-"));
+		try {
+			const longContent = `const x = "${"Z".repeat(5000)}";`;
+			const csJson = JSON.stringify([
+				{
+					filename: "big.ts",
+					location: join(workDir, "big.ts"),
+					score: 1,
+					language: "TypeScript",
+					lines: [{ line_number: 1, content: longContent, match_positions: [[10, 14]] }],
+				},
+			]);
+			process.env.DISPATCH_CS_BIN = writeStub(stubDir, ECHO_ENV_STUB);
+			process.env.CS_STUB_OUTPUT = csJson;
+			const tool = createSearchCodeTool(workDir);
+			const out = await tool.execute({ query: "x" });
+			expect(out).toContain("line truncated");
+			// No single output line should approach the raw 5k length.
+			const longest = Math.max(...out.split("\n").map((l) => l.length));
+			expect(longest).toBeLessThan(700);
+		} finally {
+			await rmP(stubDir, { recursive: true, force: true });
+		}
+	});
+
 	it("surfaces raw output when cs returns unparseable JSON", async () => {
 		const stubDir = await mkdtempP(join(tmpdir(), "dispatch-cs-stub-"));
 		try {