fix: Export silently yields zero GDR/DTR rows when result fits in initial QSqlQueryModel batch (closes #177)

[seam0814]

Summary

getDatalogForReport() is a generator the Excel exporter uses to
stream GDR/DTR rows out of the tmodel_datalog Qt model. The
previous shape silently yielded zero rows whenever the entire
query result fit in QSqlQueryModel's initial prefetch batch
(default 256 rows). DTR/GDR records in a typical STDF file are well
under 256, so the GDR & DTR Summary sheet always came out blank even
though the data was in the DB — exactly the symptom in #177. The
"Convert STDF to XLSX" path goes through DatabaseFetcher.getDTR_GDRs
which executes the SQL directly, and so was unaffected.

Closes #177.

Root cause

# previous
row = 0
while model.canFetchMore():        # <-- already False if result ≤ 256 rows
    model.fetchMore()
    while row < model.rowCount():
        ...
        yield datalogRow

QSqlQueryModel pre-populates up to 256 rows on setQuery().
canFetchMore() returns True only if there are more rows beyond
that initial batch. So for small result sets the outer loop never
runs and the generator yields nothing.

Change

# new
row = 0
while True:
    while row < model.rowCount():
        ...
        yield datalogRow
    if not model.canFetchMore():
        break
    model.fetchMore()

Yield current rows first, then fetch more, repeat until exhausted.
Streaming behaviour is preserved for large result sets; the small-
result-set case now drains the rows that are already in the model.

Verification

Reproduced and verified deterministically using a FakeModel that
mimics QSqlQueryModel's 256-row prefetch:

total=   0 | old yielded=   0 [ok ] | new yielded=   0 [ok]
total=   1 | old yielded=   0 [BUG] | new yielded=   1 [ok]
total=   5 | old yielded=   0 [BUG] | new yielded=   5 [ok]
total= 100 | old yielded=   0 [BUG] | new yielded= 100 [ok]
total= 256 | old yielded=   0 [BUG] | new yielded= 256 [ok]
total= 257 | old yielded= 257 [ok ] | new yielded= 257 [ok]
total= 500 | old yielded= 500 [ok ] | new yielded= 500 [ok]
total=1000 | old yielded=1000 [ok ] | new yielded=1000 [ok]

(The repo has no automated test harness, so this was static
reproduction; if you have a sample STDF with DTR records that
previously reproduced #177, the same file should now produce a
populated GDR & DTR Summary sheet on Export.)

Scope

getDatalogForReport is only called from
stdfExporter.getTableDataFromParent in
deps/uic_stdExporter.py, so the change is scoped to the Export
path. The in-GUI GDR & DTR table iterates the model directly via
tmodel_datalog and was not affected by the bug.

[noonchen]

Code changes seem good, only need to update the comment :)

[noonchen-ni]

@seam0814 could you please update the comments as suggested? thanks!

[seam0814]

Updated and pushed (db25269). Inline comment trimmed and the # method 1 block restored as requested — thanks for the review!

[noonchen]

@seam0814 thanks for your contribution! merged.

The windows build error might be related to msvc version or other reasons, ignored for now.