docs(triage): six open issues, and where three of the reports are wrong about the cause

#564, #597, #599, #603, #604, #606 read against the code and measured where a
claim was checkable. Every report is accurate about its symptom; three are
wrong about the cause, and two of those describe a smaller defect than the one
present:

  #606  the scanner has never had block-comment state -- `git log -S` returns
        no such commit -- so the bisect dates when the defect became audible,
        not when it was introduced. The refusal added at 2026.9.9.1 is correct.
        The unreported form is worse and was measured: `export module y;`
        inside a block comment makes a plain `.cpp` the recorded producer of a
        BMI the compiler never writes, and a real importer of `y` is then told
        `imports must be built before being imported`.

  #604  cause read rather than guessed: the host-module flag de-duplicator is
        per token and was written for GCC's one-token `-fmodules`. MSVC's
        reference is two tokens whose first legitimately repeats, so the pair
        loses its `/reference` and cl reads `<name>=<path>` as a source file.

  #599  three defects, not two: the hub path is stale (and the report's
        replacement path is also wrong), the `uninit` branch prints a note that
        cannot turn a job red, and there is no bench workflow at all -- so the
        check has run in zero CI jobs since it was written.

#603's suggested fix needs one correction: the existing probe reads
`tc.version`, which is clang's on that path, against an MSVC threshold. #564's
two dead keys want opposite answers. #597 is largely implemented on the #605
line; its remaining two items reuse existing mechanism.

Author: speak-agent