feat(logging)!: make C5 session logging opt-in

Session logging is the one opinionated category that writes a persistent
record of terminal output to disk, and those logs can contain secrets.
Silent-by-default is the wrong posture for it, so C5 now defaults to off:
__fish_config_op_logging must be set to an explicit truthy value to enable
capture, and the master switch cannot enable it on its own.

Implemented as a single special case in __fish_config_op_enabled, so all
five capture components, the sentinel file, the paru/yay wrappers, the
Kitty watcher, and the config-settings TUI pick it up with no other code
changes. The existing startup sync in conf.d/logging-events.fish
reconciles the sentinel and removes the generated wrappers on the first
shell after upgrading.

BREAKING CHANGE: users relying on the previous default must now run
`set -U __fish_config_op_logging on`. Existing logs in ~/.terminal_history
are left untouched.

docs/manual/00-table-of-contents.md

@@ -45,7 +45,7 @@ sidebar:
     11. Troubleshooting
         11.1 Uninstalling and Reverting to Backup
         11.2 Fish Version Requirement
-        11.3 Disable Session Logging
+        11.3 Enable or Disable Session Logging
         11.4 Change or Disable the Greeting
         11.5 Secrets and Machine-Local Configuration
         11.6 Tool Init Does Nothing (Return Sentinel)