feat(cicero-core): compress .cta archives with DEFLATE

[yashhzd]

Summary

Fixes #678

.cta template archives are currently created with STORE (no compression), producing files roughly 2x larger than necessary. As noted by @jeromesimeon, JSZip defaults to STORE when no compression option is passed.

This PR enables DEFLATE compression in TemplateSaver.toArchive() and expands test coverage from 2 to 16 test cases.

Changes

1. Enable DEFLATE compression

// Before — no compression (STORE)
return zip.generateAsync({
    type: 'nodebuffer'
}).then(something => {
    return Promise.resolve(something).then(result => {
        return result;
    });
});

// After — DEFLATE level 6
return zip.generateAsync({
    type: 'nodebuffer',
    compression: 'DEFLATE',
    compressionOptions: {
        level: 6
    }
});

Level 6 provides a good balance between compression ratio and speed (level 9 is only marginally smaller but significantly slower).

2. Clean up redundant Promise wrapping

The previous code wrapped generateAsync's result in an unnecessary Promise.resolve().then() chain that just returned the value unchanged. Simplified to a direct return.

3. Remove unused archiver devDependency

The archiver package (v5.3.1) was declared in devDependencies but never imported or used anywhere in the codebase. Removed to reduce install size and maintenance burden.

4. Expand TemplateSaver test coverage (2 → 16 tests)

TemplateSaver previously had only 2 tests. This PR adds 14 new tests across 4 categories:

Compression tests (2):

Test	What it validates
DEFLATE verification	Archive files use DEFLATE compression (magic \x08\x00)
Size comparison	Compressed archive is smaller than uncompressed equivalent

Archive structure tests (7):

Test	What it validates
package.json	Present with correct template name
model/ directory	Contains model files
grammar template	text/grammar.tem.md present and non-empty
sample text	text/sample.md present
logic/ directory	Directory entry exists in archive
request.json	Present when metadata includes request data
README.md	Present when metadata includes README
No signature	signature.json absent when template is unsigned

Backward compatibility tests (3):

Test	What it validates
Roundtrip load	Compressed archive loads via Template.fromArchive() with matching identifier and model count
Uncompressed .cta	Pre-existing STORE archives still load correctly
Content preservation	Template grammar and sample text survive compress→decompress roundtrip

Logo test (1):

Test	What it validates
Binary logo	logo.png included as binary in archive

All 192 tests pass (including 16 TemplateSaver tests). 7 pre-existing pending tests (template signing) unaffected.

Backward Compatibility

This is not a breaking change. JSZip's loadAsync() transparently handles both STORE and DEFLATE archives. The test suite explicitly verifies that:

1. New compressed archives load correctly via Template.fromArchive()
2. Pre-existing uncompressed .cta files continue to load without error
3. Template content (grammar, samples, models) survives the roundtrip

As @mttrbrts asked in the original issue — this is safe because the reading side (JSZip) auto-detects compression format.

Author Checklist

• Code compiles and all 192 tests pass
• 14 new tests added (2 → 16 total for TemplateSaver)
• Backward compatibility verified with existing .cta archives
• Unused dependency removed
• Signed-off-by for DCO