fix(emulate): correct Firefox 147+ Accept-Language q-value

[luamz]

Closes #177.

Firefox 147 changed how Accept-Language q-values are generated. The list used to divide 1.0 across its entries, giving q=0.5 for a two-entry list, and now decrements by 0.1 per entry, giving q=0.9.

• Bugzilla 2000765 (target milestone: 147 Branch)
• Landed in mozilla-firefox 0e050ae5116d

The Firefox 147 through 152 profiles still emit the pre-147 value, so they differ from the browser they emulate by that one header.

Changes

• header_firefox_accept! gains a zstd_q09 arm, and the arms now share a common @build arm instead of repeating the three inserts
• new header_initializer_with_zstd_q09, identical to header_initializer_with_zstd apart from the q-value
• Firefox 147 through 152 point at it; every profile below 147 is untouched
• a test asserts the expected value for all 21 Firefox profiles, listed individually rather than as a range, so adding a profile is a deliberate choice about which side of 147 it falls on

Note on CI

crates/wreq-util is not a workspace member, so CI compiles it as a patched dependency but does not execute its test targets. The added test was run locally against the wreq rev this branch pins, both with and without emulation-compression.

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