chore: bump version to 0.7.7

[vigneshnarayanaswamy]

Release the delta since v0.7.6:

• feat(snowflake): self-heal on auth-token expiry via connection_factory #24 — SnowflakeLedgerBackend self-heals on auth-token expiry (errno 390114) via an optional connection_factory: fresh connection + single retry of the same statement. The permanent fix for the recurring long-idle 500s that client_session_keep_alive (shipped in the API's fix: stabilize the package — version, CI, connector discovery #13) only mitigates.
• perf(sdk): batch edge resolution in the investigate/graph hot path #25 — batched edge resolution in the investigate/graph hot path.

After merge: cut the v0.7.7 GitHub release (CI publishes on release: published), then repin model-ledger-api to 0.7.7.