Undocumented -x (xtrace) wrapper flag

[codeforester]

Problem

basectl --help shows a real, wired-up wrapper-level flag that isn't documented anywhere:

-x  Enable Bash xtrace before running the command

Confirmed wired in cli/bash/commands/basectl/basectl.sh:848,851 (getopts ":hvx" ... x) set -x ;;). It is not mentioned in docs/command-reference.md, docs/execution-model.md, or docs/stability-tiers.md's public/internal wrapper-option lists -- those docs document -v and --keep-temp but not -x.

Why this matters

-x is exactly the kind of flag a contributor debugging a Bash-layer issue would want to know about (it's the wrapper-level xtrace switch, distinct from -v's DEBUG logging and --debug-wrapper's pre-runtime diagnostics) -- but it's currently only discoverable via --help itself, not the docs that specifically catalog wrapper options.

Related: #1606 (open) proposes a canonical command-metadata source to prevent flag documentation from silently diverging from --help output; this issue is the concrete current gap.

Proposed change

Add -x to the wrapper-option documentation in docs/command-reference.md, docs/execution-model.md, and docs/stability-tiers.md's public option lists, alongside the existing -v/--keep-temp entries.

Acceptance criteria

• -x is documented in the wrapper-option reference alongside the other public wrapper flags.