test(fetch): stealth regression suite against 5 public detection sites

Adds stealth_test.rs with 5 integration tests that verify Palimpsest's
anti-detection patches against known public bot detection test sites:

1. Sannysoft (bot.sannysoft.com) — classic 13-point headless battery
   Asserts: webdriver, chrome object, plugins, languages pass

2. Infosimples (detect-headless) — 16-point detection with DOM parsing
   Asserts: webdriver, chrome element, plugins, languages, permissions pass

3. FingerprintJS BotD — 18 detectors with structured output
   Reports: all detector results, overall bot verdict

4. Rebrowser Bot Detector — CDP Runtime.enable leak detection
   Parses: #detections-json textarea (JSON array with ratings)
   Reports: each detection type with pass/fail rating

5. CreepJS — advanced stealth detection (chrome object position,
   proxy traps, lie detection, cross-context consistency)
   Reports: crowd blending score, headless ratings, lie count

Tests are #[ignore] by default — they require Chrome + network:
  cargo test -p palimpsest-fetch --test stealth_test -- --ignored --nocapture

Each test launches a fresh stealth-hardened Chrome instance with all
17 evasion patches injected, navigates to the detection site, extracts
machine-readable results, and asserts critical checks pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: copyleftdev

crates/palimpsest-fetch/Cargo.toml

@@ -33,5 +33,7 @@ palimpsest-frontier = { path = "../palimpsest-frontier" }
 palimpsest-index = { path = "../palimpsest-index" }
 palimpsest-storage = { path = "../palimpsest-storage" }
 palimpsest-replay = { path = "../palimpsest-replay" }
+futures = "0.3"
+serde_json = { workspace = true }
 tokio = { workspace = true, features = ["rt", "macros"] }
 wiremock = { workspace = true }