Skip fuzzy search for exact normalized matches

[harshitgupta31415]

Fixes #1390

When a message only changes capitalization or surrounding whitespace, its fuzzy key can already be in the candidate dictionary. This checks that dictionary first instead of comparing the text with every candidate again.

The existing search gives identical normalized strings a score of 1, so the shortcut picks the same key. The merge code is unchanged: translations, fuzzy flags, comments, previous IDs and obsolete messages still go through the same path. Actual wording changes still use get_close_matches(). No extra cache is added.

For Q exact-normalized lookups among C candidates, this avoids Q × C candidate comparisons and uses Q dictionary lookups instead, after the existing candidate preparation. String normalization still takes time, and nonexact fuzzy matching has the same complexity as before. This does not make every catalog update linear.

This leaves the current normalized-key collision behavior alone; #1330 handles that separately.

Checks:

• 419 before/after comparisons matched, covering update options, plurals, Unicode, empty normalized text, collisions, comments, flags, previous IDs, obsolete messages and template contents.
• The full suite ran on both implementations. PR: 7,835 passed; base: 7,834 passed. Both had the same two failures in test_get_timezone_name_misc on this Windows machine (GMT+00:00 versus GMT+05:30), plus 9 skips and 2 expected failures. The base run excludes the new test that specifically checks fuzzy-search call elimination.
• Ruff and git diff --check pass. The full messages tests pass on both versions.

Benchmark scripts, raw samples and reproduction steps.

All 40 benchmark rows, including controls and slower results

Measurements use Python 3.14.5 on Windows. Each row uses one fixed pair of physical cores; pairs rotate between rows. These Python functions are single-threaded, not parallel workers. Results from different pairs are shown separately because this laptop has different core types.

Each row has five paired timing samples per version (short calls batched), plus five separate tracemalloc measurements. Times and peaks are medians. GC stays enabled. Peaks cover newly traced Python allocations during the call, not total process RAM or a copy of the installed library.

The full workflow parses existing PO bytes, updates from a prepared template, and writes the entire PO. Reading files and preparing the template are outside the measurement. The catalogs are real Django/Wagtail translations; the edits are controlled capitalization, surrounding-whitespace, or punctuation changes, not production traffic.

All output bytes matched. The unchanged and punctuation-change controls do not use the shortcut, so their timing differences are not claimed as improvements. Every measured row is included, including slower results.

Catalog / edits	Messages	CPU mask	Base time	PR time	Speed	Base peak	PR peak	Memory
Django German: unchanged	348	0xf0	13.823 ms	12.249 ms	1.129× faster	591.587 KiB	591.595 KiB	1.000013× more
Django German: unchanged	348	0x300	55.629 ms	52.144 ms	1.067× faster	591.587 KiB	591.595 KiB	1.000013× more
Django German: unchanged	348	0xc00	49.053 ms	50.224 ms	1.024× slower	591.587 KiB	591.595 KiB	1.000013× more
Django German: unchanged	348	0xf	32.276 ms	28.641 ms	1.127× faster	591.587 KiB	591.595 KiB	1.000013× more
Django German: 1 capitalization edit	348	0xf0	29.950 ms	28.073 ms	1.067× faster	592.126 KiB	591.714 KiB	1.000696× less
Django German: 1 capitalization edit	348	0x300	54.517 ms	54.585 ms	1.001× slower	592.126 KiB	591.714 KiB	1.000696× less
Django German: 1 capitalization edit	348	0xc00	53.022 ms	49.043 ms	1.081× faster	592.126 KiB	591.714 KiB	1.000696× less
Django German: 1 capitalization edit	348	0xf	30.010 ms	25.383 ms	1.182× faster	592.126 KiB	591.714 KiB	1.000696× less
Django German: 20 capitalization edits	348	0xf0	56.788 ms	25.472 ms	2.229× faster	595.118 KiB	593.871 KiB	1.002100× less
Django German: 20 capitalization edits	348	0x300	120.036 ms	55.460 ms	2.164× faster	595.118 KiB	593.871 KiB	1.002100× less
Django German: 20 capitalization edits	348	0xc00	110.024 ms	51.596 ms	2.132× faster	595.118 KiB	593.871 KiB	1.002100× less
Django German: 20 capitalization edits	348	0xf	66.644 ms	30.773 ms	2.166× faster	595.118 KiB	593.871 KiB	1.002100× less
Django German: 20 whitespace edits	348	0xf0	28.975 ms	12.799 ms	2.264× faster	595.118 KiB	593.871 KiB	1.002100× less
Django German: 20 whitespace edits	348	0x300	104.334 ms	40.984 ms	2.546× faster	595.118 KiB	593.871 KiB	1.002100× less
Django German: 20 whitespace edits	348	0xc00	85.013 ms	37.325 ms	2.278× faster	595.118 KiB	593.871 KiB	1.002100× less
Django German: 20 whitespace edits	348	0xf	35.395 ms	13.387 ms	2.644× faster	595.118 KiB	593.871 KiB	1.002100× less
Django German: 5 punctuation edits	348	0xf0	15.188 ms	15.417 ms	1.015× slower	592.829 KiB	592.889 KiB	1.000100× more
Django German: 5 punctuation edits	348	0x300	47.487 ms	47.451 ms	1.001× faster	592.829 KiB	592.889 KiB	1.000100× more
Django German: 5 punctuation edits	348	0xc00	47.463 ms	47.364 ms	1.002× faster	592.829 KiB	592.889 KiB	1.000100× more
Django German: 5 punctuation edits	348	0xf	37.621 ms	42.823 ms	1.138× slower	592.829 KiB	592.889 KiB	1.000100× more
Wagtail French: unchanged	902	0xf0	75.059 ms	73.486 ms	1.021× faster	1488.002 KiB	1488.010 KiB	1.000005× more
Wagtail French: unchanged	902	0x300	146.674 ms	147.000 ms	1.002× slower	1488.002 KiB	1488.010 KiB	1.000005× more
Wagtail French: unchanged	902	0xc00	134.303 ms	141.306 ms	1.052× slower	1488.002 KiB	1488.010 KiB	1.000005× more
Wagtail French: unchanged	902	0xf	105.319 ms	81.885 ms	1.286× faster	1488.002 KiB	1488.010 KiB	1.000005× more
Wagtail French: 1 capitalization edit	902	0xf0	91.610 ms	91.494 ms	1.001× faster	1489.104 KiB	1488.127 KiB	1.000656× less
Wagtail French: 1 capitalization edit	902	0x300	153.530 ms	152.039 ms	1.010× faster	1489.104 KiB	1488.127 KiB	1.000656× less
Wagtail French: 1 capitalization edit	902	0xc00	140.547 ms	139.960 ms	1.004× faster	1489.104 KiB	1488.127 KiB	1.000656× less
Wagtail French: 1 capitalization edit	902	0xf	86.034 ms	89.647 ms	1.042× slower	1489.104 KiB	1488.127 KiB	1.000656× less
Wagtail French: 20 capitalization edits	902	0xf0	307.301 ms	72.262 ms	4.253× faster	1493.002 KiB	1490.275 KiB	1.001830× less
Wagtail French: 20 capitalization edits	902	0x300	589.803 ms	172.948 ms	3.410× faster	1493.002 KiB	1490.275 KiB	1.001830× less
Wagtail French: 20 capitalization edits	902	0xc00	520.951 ms	127.837 ms	4.075× faster	1493.002 KiB	1490.275 KiB	1.001830× less
Wagtail French: 20 capitalization edits	902	0xf	314.200 ms	76.707 ms	4.096× faster	1493.002 KiB	1490.275 KiB	1.001830× less
Wagtail French: 20 whitespace edits	902	0xf0	309.306 ms	96.431 ms	3.208× faster	1493.002 KiB	1490.275 KiB	1.001830× less
Wagtail French: 20 whitespace edits	902	0x300	539.413 ms	137.014 ms	3.937× faster	1493.002 KiB	1490.275 KiB	1.001830× less
Wagtail French: 20 whitespace edits	902	0xc00	529.044 ms	137.946 ms	3.835× faster	1493.002 KiB	1490.275 KiB	1.001830× less
Wagtail French: 20 whitespace edits	902	0xf	294.051 ms	74.587 ms	3.942× faster	1493.002 KiB	1490.275 KiB	1.001830× less
Wagtail French: 5 punctuation edits	902	0xf0	125.129 ms	115.699 ms	1.082× faster	1490.213 KiB	1490.278 KiB	1.000044× more
Wagtail French: 5 punctuation edits	902	0x300	258.087 ms	265.939 ms	1.030× slower	1490.213 KiB	1490.278 KiB	1.000044× more
Wagtail French: 5 punctuation edits	902	0xc00	206.512 ms	211.068 ms	1.022× slower	1490.213 KiB	1490.278 KiB	1.000044× more
Wagtail French: 5 punctuation edits	902	0xf	122.132 ms	118.546 ms	1.030× faster	1490.213 KiB	1490.278 KiB	1.000044× more

Base commit: e2a1791. Source, runner and fixture hashes and every raw sample are in the linked JSON.

Fixtures (downloaded from these pinned sources; not copied into the benchmark gist):

• Django German
• Wagtail French