fix(tui): use canonical get_fallback_chain for parity + map author

Follow-up to the salvaged fallback-chain fix:
- Replace the hand-rolled fallback loader with the shared
  hermes_cli.fallback_config.get_fallback_chain() helper so the TUI path
  matches HermesCLI and gateway/run.py exactly: fallback_providers stays
  first and keeps order, with distinct legacy fallback_model entries
  merged in after (deduped). Previously the TUI loader picked one key OR
  the other, diverging from CLI/gateway when both were set.
- Update the test to assert the merged canonical semantics.
- Add psionic73 to scripts/release.py AUTHOR_MAP (CI gate).

scripts/release.py

@@ -58,6 +58,7 @@ AUTHOR_MAP = {
     "thomas.paquette@gmail.com": "RyTsYdUp",
     "techxacm@gmail.com": "ProgramCaiCai",
     "266365592+bmoore210@users.noreply.github.com": "bmoore210",
+    "157839748+psionic73@users.noreply.github.com": "psionic73",
     "manishbyatroy@gmail.com": "manishbyatroy",
     "chilltulpa@gmail.com": "TheGardenGallery",
     "al@randomsnowflake.me": "randomsnowflake",