docs(readme): add USACO and Kattis to supported platforms list

Problem: Submit used fixed `wait_for_timeout` delays throughout, and the
practice fallback check only matched one dialog variant, causing "contest
not available for submission" to be silently swallowed as success.

Solution: Replace the initial 2s page-load sleep with
`wait_for_selector('[aria-haspopup="listbox"]')`, drop unnecessary sleeps
around the Ace editor click and submit button, and wait for the result
dialog with `wait_for_selector` instead of a fixed 3s sleep. Extend the
fallback check to also match "not available for submission".

README.md

@@ -9,7 +9,8 @@ https://github.com/user-attachments/assets/e81d8dfb-578f-4a79-9989-210164fc0148
 
 ## Features
 
-- **Multi-platform support**: AtCoder, CodeChef, Codeforces, and CSES
+- **Multi-platform support**: AtCoder, CodeChef, Codeforces, USACO, CSES,
+  Kattis
 - **Automatic problem setup**: Scrape test cases and metadata in seconds
 - **Dual view modes**: Lightweight I/O view for quick feedback, full panel for
   detailed analysis

scrapers/atcoder.py

@@ -30,7 +30,6 @@ from .timeouts import (
     BROWSER_ELEMENT_WAIT,
     BROWSER_NAV_TIMEOUT,
     BROWSER_SESSION_TIMEOUT,
-    BROWSER_SETTLE_DELAY,
     BROWSER_SUBMIT_NAV_TIMEOUT,
     BROWSER_TURNSTILE_POLL,
     HTTP_TIMEOUT,
@@ -500,7 +499,6 @@ def _submit_headless(
                     "buffer": Path(file_path).read_bytes(),
                 },
             )
-            page.wait_for_timeout(BROWSER_SETTLE_DELAY)
             page.locator('button[type="submit"]').click(no_wait_after=True)
             page.wait_for_url(
                 lambda url: "/submissions/me" in url,

scrapers/codechef.py

@@ -178,16 +178,15 @@ def _submit_headless_codechef(
             needs_relogin = True
             return
         try:
-            page.wait_for_timeout(2000)
+            page.wait_for_selector('[aria-haspopup="listbox"]', timeout=10000)
 
             page.locator('[aria-haspopup="listbox"]').click()
             page.wait_for_selector('[role="option"]', timeout=5000)
             page.locator(f'[role="option"][data-value="{language_id}"]').click()
-            page.wait_for_timeout(2000)
+            page.wait_for_timeout(250)
 
             page.locator(".ace_editor").click()
             page.keyboard.press("Control+a")
-            page.wait_for_timeout(200)
             page.evaluate(
                 """(code) => {
                     const textarea = document.querySelector('.ace_text-input');
@@ -199,20 +198,25 @@ def _submit_headless_codechef(
                 }""",
                 source_code,
             )
-            page.wait_for_timeout(1000)
+            page.wait_for_timeout(125)
 
             page.evaluate(
                 "() => document.getElementById('submit_btn').scrollIntoView({block:'center'})"
             )
-            page.wait_for_timeout(200)
             page.locator("#submit_btn").dispatch_event("click")
-            page.wait_for_timeout(3000)
+            try:
+                page.wait_for_selector('[role="dialog"], .swal2-popup', timeout=5000)
+            except Exception:
+                pass
 
             dialog_text = page.evaluate("""() => {
                 const d = document.querySelector('[role="dialog"], .swal2-popup');
                 return d ? d.textContent.trim() : null;
             }""")
-            if dialog_text and "not available for accepting solutions" in dialog_text:
+            if dialog_text and (
+                "not available for accepting solutions" in dialog_text
+                or "not available for submission" in dialog_text
+            ):
                 submit_error = "PRACTICE_FALLBACK"
             elif dialog_text:
                 submit_error = dialog_text

scrapers/timeouts.py

@@ -11,4 +11,3 @@ BROWSER_SUBMIT_NAV_TIMEOUT["atcoder"] = BROWSER_NAV_TIMEOUT * 2
 BROWSER_SUBMIT_NAV_TIMEOUT["codeforces"] = BROWSER_NAV_TIMEOUT * 2
 BROWSER_TURNSTILE_POLL = 5000
 BROWSER_ELEMENT_WAIT = 10000
-BROWSER_SETTLE_DELAY = 500