Move JTAG exporters to factory functions and rename console to ostream #121

Parent

#15

What to build

Move every exporter onto factory functions, and give the Ostream exporter family one name, so the ESP log exporter can follow a single convention from its first commit.

• The JTAG exporters for spans, log records, metrics and profiles are created only through MakeJtagSpanExporter(), MakeJtagLogRecordExporter(), MakeJtagMetricExporter() and MakeJtagProfilesExporter(). The classes are private to the implementation, with no compatibility aliases, since every caller is in this repository. Signal gating and runtime behaviour are unchanged.
• The Ostream profiles factory MakeConsoleProfilesExporter() becomes MakeOstreamProfilesExporter().
• The Kconfig label "Console (ostream) exporters" becomes "Ostream exporters". The option's symbol is unchanged.

See the parent spec, section "Preparatory alignment".

Acceptance criteria

• The JTAG exporters can be created only through the four MakeJtag*Exporter() factories; the public header declares no JTAG exporter classes.
• Each JTAG factory for a signal is available only when that signal is enabled; MakeJtagProfilesExporter() is not gated on a signal.
• MakeOstreamProfilesExporter() replaces MakeConsoleProfilesExporter(), and the old name no longer exists.
• The Kconfig menu shows "Ostream exporters"; existing sdkconfig files keep working without changes.
• The JTAG example, the profiles example, the README's tables and every header comment use the new names; no reference to the old class or factory names remains outside third-party code.
• The JTAG example builds in CI.
• The profiles example passes its QEMU test unchanged.
• All CI jobs pass.

Blocked by

None (can start immediately).