feat: password Realm, single-chair login, shared parliament context (0.9.12)

Derive Realm keys from a user password (Argon2id, no private key on disk).
Login claims the sole chair with handover; peers share parliament context;
--new-project clears it. CLI peer/discover helpers and Docker alpine recipe
included; headless empty-answer retries raised for unattended runs.

Co-authored-by: Cursor <cursoragent@cursor.com>

.dockerignore

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+.git
+result
+build/
+build-*/
+dist/
+third_party/
+backups/
+reports/
+*.o
+*.a
+cst-agent
+tests/test_*
+!tests/test_*.c
+app/
+.cursor/
+*.apk
+*.tar.gz