Excel compares and shows numbers to 15 significant digits, but it writes the cached value of a formula to the file at full double precision. =0.1+0.2 is stored as 0.30000000000000004 and =1.1*1.1-1 as 0.21000000000000019, while Excel shows 0.3 and 0.21. parsers::spreadsheet prints the double in Rust's shortest round-trip form. That form keeps the tail whenever the computed double is not the one nearest the decimal.

Problem

A sheet with cached values the way Excel writes them, read on dev 2e7ba78:

| 合计 | 0.30000000000000004 |
| 增长率 | 0.2100000000000002 |

• The text, the evidence quote and any value extracted from these rows carry digits the person never sees.
• A search for 0.21 does not meet 0.2100000000000002.
• Values Excel stored as the double nearest their decimal already read clean: 1395.0527999999999 reads 1395.0528, and 19.899999999999999 reads 19.9. Only computed values keep a tail.

Change

parsers::spreadsheet writes a Data::Float cell with excel_number: the value is rounded to 15 significant digits, then printed in its shortest decimal form.

• Values that were already clean (19.9, 1200, 45306) read exactly as before.
• Integers stay integers.
• Non-finite values are left alone.
• A value with more than 15 significant digits, which Excel itself cannot hold, is written to the 15 that Excel shows.

The new arm sits next to excel_date (#1017).

Verification

Run on macOS (arm64): Rust 1.98.1; the workspace suite against PostgreSQL 16 with pgvector 0.8.2, with Poppler 26.06.

crates/utopia-ingest/tests/spreadsheet_numbers.rs builds an .xlsx with values written the way Excel caches them, under the General format:

• a_computed_number_reads_with_the_digits_excel_keeps: 0.3, 0.21 and -0.3. On dev with only this file added it fails with 0.30000000000000004, 0.2100000000000002 and -0.30000000000000004.
• a_number_that_was_already_clean_reads_as_before: 1395.0528, 19.9, 1200, 123456789012345000 and 0.125. It passes on dev and here.

Other checks:

• The openpyxl ledger from A date in a spreadsheet is read as the date it shows, not as Excel's day count #1017 reads exactly as before.
• cargo test --locked -p utopia-ingest: 125 passed.
• cargo fmt --all --check and cargo clippy --locked --workspace --all-targets -- -D warnings are clean.
• UTOPIA_TEST_REQUIRE_DB=1 UTOPIA_TEST_REQUIRE_PDFTOTEXT=1 cargo test --locked --workspace: 1,345 passed, 0 failed, 6 ignored. That run had this change merged with the Word non-breaking-hyphen fix opened alongside it.

Not in this change

A cell formatted as a percentage still reads as its fraction (0.125, not 12.5%). calamine gives no number format for cells that are not dates.