`libfec fastfec` panics on filings with `[BEGINTEXT]`/`[ENDTEXT]` records

[asg017]

Note

Much of this ticket was composed with Claude

Description

When processing large filings that contain [BEGINTEXT]/[ENDTEXT] blocks (used for F99 miscellaneous text and TEXT records), libfec fastfec panics with:

thread 'main' panicked at crates/fec-cli/src/commands/fastfec.rs:89:18:
CSV position to be available

The [BEGINTEXT]/[ENDTEXT] handler in Filing::next_row() constructs a new StringRecord from the text content, but this record lacks the CSV byte-position metadata. The progress bar code then calls .expect() on the missing position.

Root Cause

fastfec.rs:86-90:

pb.set_position(
    r.record
        .position()
        .expect("CSV position to be available")
        .byte(),
);

Records emitted from [BEGINTEXT]/[ENDTEXT] processing (in lib.rs:344-382) are constructed from the next record after [ENDTEXT], which may not have position info depending on the CSV reader state.

Affected Filing

Filing ID: 1947601 (130MB, Trump for President F3PA filing FEC-1434701)

Reproduction

# libfec panics:
libfec fastfec ~/.cache/libfec/cache/1947601.fec /tmp/out_libfec
# thread 'main' panicked at crates/fec-cli/src/commands/fastfec.rs:89:18:
# CSV position to be available

# FastFEC succeeds:
fastfec --no-stdin ~/.cache/libfec/cache/1947601.fec /tmp/out_fastfec
# Done; parsing successful!

Observe the Difference

# libfec produces no output (panics before completing):
ls /tmp/out_libfec/1947601/ 2>/dev/null || echo "directory incomplete or missing"

# FastFEC produces full output:
ls /tmp/out_fastfec/1947601/
# F3PA.csv  SA20A.csv  SB23.csv  SB29.csv  SD12.csv  TEXT.csv  header.csv

Suggested Fix

Replace .expect("CSV position to be available") with a fallback:

if let Some(pos) = r.record.position() {
    pb.set_position(pos.byte());
}

(NOTE: wait no, we can copy the position data from the original StringRecord to the new one, right?)