feat(playwright): adopt per-thread sessions for shared Chrome automation

AGENTS.md

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+# AGENTS.md
+
+## XiaoHongShu / Playwright Hard Rules
+
+These rules are mandatory for any workflow that uses `tools/pw` (directly or indirectly).
+
+1. Preflight before first browser action:
+   - Run `tools/pw --help` once with escalation (`sandbox_permissions=require_escalated`).
+2. All `tools/pw ...` commands (including browse/like/comment/reply flows) must be executed with escalation (`sandbox_permissions=require_escalated`) by default.
+3. If preflight or any `tools/pw ...` command still fails with network sandbox signatures, rerun the same command with escalation immediately:
+   - `ENOTFOUND`
+   - `EAI_AGAIN`
+   - `ETIMEDOUT`
+   - `ECONNREFUSED`
+   - `registry.npmjs.org` fetch failure
+4. Do not continue XiaoHongShu actions (browse/like/comment/reply) until preflight succeeds.
+5. Do not try alternate non-escalated workarounds for `tools/pw`.