chore: release v0.21.0

[Alex793x]

🤖 New release

• syncable-cli: 0.20.0 -> 0.21.0 (⚠ API breaking changes)

⚠ syncable-cli breaking changes

--- failure constructible_struct_adds_field: externally-constructible struct adds field ---

Description:
A pub struct constructible with a struct literal has a new pub field. Existing struct literals must be updated to include the new field.
        ref: https://doc.rust-lang.org/reference/expressions/struct-expr.html
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.45.0/src/lints/constructible_struct_adds_field.ron

Failed in:
  field ChatSession.token_usage in /tmp/.tmpjrF1p7/syncable-cli/src/agent/session.rs:46

Changelog

0.21.0 - 2025-12-16

Added

• updated agent layer, with better ui for interactivness

Other

• Merge pull request feat: updated agent layer, with better ui for interactivness #189 from syncable-dev/develop

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