Fix daily note weekday completion aliases

[devin-ai-integration]

Summary

Fixes daily-note completions so tomorrow/yesterday also expose their weekday aliases, matching workspace command behavior:

• tomorrow now also has a next <weekday> completion alias.
• yesterday now also has a last <weekday> completion alias.
• Daily-note completions can now produce multiple display/filter aliases for the same underlying date while inserting the same date ref.
• Adds unit tests for the tomorrow/next weekday and yesterday/last weekday cases.

Fixes #420

Review & Testing Checklist for Human

• Verify in an editor completion menu that, on a Friday, both tomorrow and next Saturday appear for the same daily note target.
• Verify selecting the alternate alias still inserts/labels the intended daily note reference.
• Check completion ordering/duplicates around existing daily-note files vs generated unresolved daily-note suggestions.

Notes

Local validation run:

• cargo fmt --check
• cargo clippy
• cargo test

Link to Devin session: https://app.devin.ai/sessions/5bac1535c3f94e018015fb068ac6400b
Requested by: @Feel-ix-343

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[devin-ai-integration]

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 3 additional findings.