xhc-hb04: rename dashed ini identifiers, migrate old configs in update_ini

[grandixximo]

The new ini parser restricts identifiers to letters, digits and underscore. The historic parser had no character restrictions, so the xhc-hb04 pendant files used dashes and no longer parse: the [XHC_HB04_BUTTONS] keys in the sample configs (start-pause, goto-zero, ...) and the [XHC-HB04] section of the pendant's own layout cfg files, which the component parses with the same IniFile class.

Per the 2026-09-27 dev meeting (conclusion in #4566), the strict identifier rule stays and the in-tree files and code are updated instead. This replaces the accept-the-dash approach of #4573.

First commit renames the dashed identifiers to underscores:

• [XHC-HB04] => [XHC_HB04] in the component's hardcoded section name, the shipped layout cfg files and the docs
• the button keys in the three sample config includes (start-pause => start_pause, goto-zero => goto_zero, ...)
• xhc-hb04.tcl maps the underscored INI button names back to the dashed HAL pin names (xhc-hb04.button-start-pause etc.), which are unchanged, so existing user HAL files referencing the pins keep working

Second commit adds the migration for existing user configs. A dashed file can not be parsed at all, and the launcher exits on the inivalue parse check before the [EMC]VERSION check that invokes update_ini, so the version-triggered path never fires. Instead update_ini gets a content-triggered text pass that runs before parsing: dashed (but otherwise valid) section and tag identifiers are rewritten with underscores in the ini file, its #INCLUDE'd files and a custom layout cfg found via a loose scan of [XHC_HB04_CONFIG]layout. Every modified file keeps a .bak copy and every rename is listed. The launcher runs this as update_ini --fix-identifiers when the parse check fails and retries afterwards, so old pendant configs migrate themselves on first boot. Identifiers that are invalid even without the dash (leading dash or digit) are left alone and fail with the original error. No THIS_VERSION bump.

One limitation: HAL files referencing [XHC_HB04_BUTTONS]start-pause through halcmd ini substitution are not rewritten. The xhc-hb04.tcl mechanism does not use such references, so this only affects hand-written HAL files.

Behavior note: the migration rewrites the user's config files on first boot without asking for confirmation. The renames are listed on stdout and a .bak copy is kept for every modified file, but a GUI user starting from a menu may never see that output. The version-based conversion path, in contrast, asks with a confirmation dialog and refuses to run without an X display. I kept the identifier fix automatic because the config does not start at all without it, the change is small and reversible, and the meeting asked for an automated update. @BsAtHome: do you want a confirmation dialog here when a display is available, like the version-based conversion has?

Testing: new tests/update_ini/dash-identifiers (ini file + included file + custom cfg + .bak + invalid identifiers), the inivalue test gains plain dash-rejection cases, full inifile suite passes 11/11. All four xhc-hb04 sample configs boot with the pendant pins and button nets present (including the std_start_pause path), and a config reverted to the old dashed form boots through the launcher and migrates itself.