Read/write schema-less KDE settings (e.g. kxkbrc's Options= line)
directly via kreadconfig6/kwriteconfig6, with default defined as the
key being absent. diff only checks freeform entries already declared
in the manifest, never via undeclared broad scan.
Brings the machine's caps-lock/Escape swap under tracking as the
real-world validation case.
Implements the broad, read-only schema-backed scan for dot kde diff:
walks every (rcfile, group, key) reachable through the kcfg mapping
table, compares live values against their schema-declared defaults,
and reports each mismatch tagged declared or undeclared. Never writes.
Also fixes dot kde completions, which only ever offered save/help —
apply (added in a prior task) and diff were both missing.
Pushes every manifest entry's declared value onto the live system via
kwriteconfig6, idempotently. Non-schema (shortcuts/freeform) entries are
rejected as not-yet-supported, deferred to later tasks.
Introduces the dot kde subcommand family (fish dispatcher plus a Python
helper under commands/kde/), a flat identifier=value manifest, and
dot kde save in both its explicit-identifier and no-argument refresh
modes. Settings resolve to KDE's KConfigXT schema-backed mechanism via a
(rcfile -> [kcfg files]) mapping table auto-derived by scanning the
system schema directory (overridable via DOT_KDE_KCFG_DIR), plus a
hand-maintained exceptions list for schemas that only declare their
target rc file at runtime. Also wires tab-completion for dot kde save
identifiers, sourced live from that same mapping table.
