Add safe URL construction rules to agent guides

Add a URL and query parameter construction section to
contrib/claude/go-style.md requiring net/url (url.JoinPath,
url.Values, url.Parse) instead of fmt.Sprintf or string
concatenation.

Create contrib/claude/ts-style.md with matching TypeScript
rules requiring URL and URLSearchParams instead of template
literals or string concatenation.

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

AGENTS.md

@@ -4,7 +4,8 @@ Detailed guides for specific subsystems live in `contrib/claude/`:
 
 - [`contrib/claude/make.md`](contrib/claude/make.md) — GNUmakefile targets, codegen, overridable variables
 - [`contrib/claude/api-surface.md`](contrib/claude/api-surface.md) — GraphQL / MCP / CLI / n8n sync rules
-- [`contrib/claude/go-style.md`](contrib/claude/go-style.md) — Go project deps, style (declarations, calls, imports, errors, naming, logging)
+- [`contrib/claude/go-style.md`](contrib/claude/go-style.md) — Go project deps, style (declarations, calls, imports, errors, naming, logging, safe URL construction)
+- [`contrib/claude/ts-style.md`](contrib/claude/ts-style.md) — TypeScript style (safe URL construction)
 - [`contrib/claude/go-testing.md`](contrib/claude/go-testing.md) — Go test conventions (parallel, require vs assert, naming)
 - [`contrib/claude/go-service.md`](contrib/claude/go-service.md) — Go service orchestration (Run, graceful shutdown, crash propagation)
 - [`contrib/claude/go-worker.md`](contrib/claude/go-worker.md) — Go worker pattern (poll-based, bounded concurrency, FOR UPDATE SKIP LOCKED)

contrib/claude/go-style.md

@@ -175,6 +175,61 @@ type ctxKey struct{ name string }
 var trustCenterIDKey = &ctxKey{name: "trust_center_id"}
 ```
 
+## URL and query parameter construction
+
+**Never** build URLs with `fmt.Sprintf`, string concatenation, or any form of string formatting. Always use the `net/url` package to construct URLs safely.
+
+- Use `url.URL` struct to build full URLs (scheme, host, path, query).
+- Use `url.Values` to build query parameters, then call `.Encode()`.
+- Use `url.QueryEscape` or `url.PathEscape` when embedding a single value into a known-safe base.
+- Use the `pkg/baseurl.URLBuilder` when constructing URLs from configured base URLs.
+
+```go
+// Bad — fmt.Sprintf
+endpoint := fmt.Sprintf("https://api.example.com/users/%s?active=%t", userID, active)
+
+// Bad — string concatenation
+endpoint := "https://api.example.com/orgs/" + orgID + "/members"
+
+// Good — url.JoinPath escapes each segment and sets Path + RawPath
+u, err := url.JoinPath("https://api.example.com", "users", userID)
+if err != nil {
+	return fmt.Errorf("cannot build URL: %w", err)
+}
+
+parsed, err := url.Parse(u)
+if err != nil {
+	return fmt.Errorf("cannot parse URL: %w", err)
+}
+
+q := parsed.Query()
+q.Set("active", strconv.FormatBool(active))
+parsed.RawQuery = q.Encode()
+
+// Good — URLBuilder from pkg/baseurl
+u, err := baseURL.URL("/users", userID).
+	Query("active", strconv.FormatBool(active)).
+	Build()
+```
+
+The same rule applies to query parameters specifically: never concatenate `"?key=" + val + "&other=" + val2`. Always use `url.Values` and assign via `RawQuery`:
+
+```go
+// Bad
+raw := baseEndpoint + "?domain=" + domain + "&limit=100"
+
+// Good
+u, err := url.Parse(baseEndpoint)
+if err != nil {
+	return fmt.Errorf("cannot parse endpoint: %w", err)
+}
+
+q := u.Query()
+q.Set("domain", domain)
+q.Set("limit", "100")
+u.RawQuery = q.Encode()
+```
+
 ## Logging
 
 `go.gearno.de/kit/log` — named, context-aware structured logging with typed fields. **Never log PII, PHI, or other sensitive data** (e.g. emails, names, passwords, tokens, health records). Log opaque identifiers (IDs, request IDs) instead. See [`contrib/claude/logging.md`](logging.md) for the full guide (allowed/forbidden data, field helpers, wiring patterns).

contrib/claude/ts-style.md

@@ -0,0 +1,32 @@
+# TypeScript Style
+
+## URL and query parameter construction
+
+**Never** build URLs with template literals, string concatenation, or string formatting. Always use the `URL` and `URLSearchParams` APIs.
+
+- Use `new URL()` to construct or parse full URLs.
+- Use `URLSearchParams` to build query strings.
+- Use `.pathname`, `.searchParams`, and other `URL` properties to modify parts of a URL safely.
+- Use `encodeURIComponent` for dynamic path segments.
+
+```typescript
+// Bad — template literal
+const endpoint = `https://api.example.com/users/${userId}?active=${active}`;
+
+// Bad — string concatenation
+const endpoint = "https://api.example.com/orgs/" + orgId + "/members";
+
+// Bad — query params via string concat
+const qs = "?domain=" + domain + "&limit=100";
+
+// Good — URL object
+const url = new URL("https://api.example.com");
+url.pathname = `/users/${encodeURIComponent(userId)}`;
+url.searchParams.set("active", String(active));
+
+// Good — URLSearchParams for query strings
+const params = new URLSearchParams();
+params.set("domain", domain);
+params.set("limit", "100");
+const qs = params.toString();
+```