Play Framework

docs: add play help enable-https / disable-https detailed help (release 1.12.20)

PF-67 follow-up: the top-level `play help` already lists enable-https
and disable-https automatically — `help.py` iterates each command
module's HELP dict, and https.py declares them correctly — but
`play help <cmd>` looks for documentation/commands/cmd-<name>.txt
for the detailed per-command help, and those files didn't exist.

Adds cmd-enable-https.txt and cmd-disable-https.txt following the
established 27-file pattern (Name / Synopsis / Description sections,
~-prefixed lines for play's output style). Covers:

- enable-https: the three steps (generate-or-reuse keystore, set
  keystore.* + https.port, set play.http2.enabled=true), idempotence,
  the dev-only keystore caveat with a pointer to swap in a real cert
  for production.

- disable-https: that both https.port and play.http2.enabled are
  commented, the keystore is preserved, and how to permanently
  remove it.

Cross-links via "See also" so users discovering one find the other.

Verified via `play help enable-https` and `play help disable-https`
on the local 1.12.20 build.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>