Draft the generic SyncProvider/SyncObserver contracts and implement
OAuthTokenBroker: valid access tokens with a five-minute refresh skew,
rotation persisted before use so a new refresh token is never lost,
400/401 refresh rejections erase the secret and surface
AccountDisconnected, and no credential material in error messages.
Add strict /me identity, atomic paged calendar discovery, and resumable primary-calendar v1 delta synchronization through the durable provider cache. Keep opaque continuations on trusted Graph URLs and retain credentials only per operation.
Document that stable Graph v1 delta covers only the primary calendar; secondary calendars still require a v1 reconciliation or beta dependency decision.
Verified: 18/18 normal, 18/18 -Werror, and 18/18 ASan/UBSan tests.
Add bounded token response parsing with refresh-token retention and a cancellable worker-thread libsecret adapter using versioned credential payloads.
Verify CRUD, isolation, cancellation, corruption, unavailable service, redaction, and cleanup against an isolated D-Bus and gnome-keyring Secret Service in normal, warning-as-error, and sanitizer profiles.
Add a bounded libcurl transport with verified TLS, no redirects or retries, sanitized failures, binary-safe requests, and resolved-address enforcement for cleartext loopback traffic.
Add shell-free xdg-open launching and a one-shot IPv4 loopback callback receiver with strict HTTP/query parsing, deadlines, fixed callback path, and RAII cleanup. Token parsing, Secret Service, and Graph remain follow-up phases.
Add a private provider-neutral SQLite WAL cache with transactional migrations, retained raw payloads and tombstones, per-window opaque checkpoints, and reserved outbox/conflict tables.
Verify migrations, permissions, identity invariants, concurrent access, atomic pull-page rollback, and future-schema rejection with deterministic tests. No OAuth, networking, secrets, or Graph synchronization is included yet.
Add a Monday-default --week-start option for every weekday and carry it through domain layout, full and compact rendering, event query windows, print mode, and the interactive TUI.
Preserve byte-compatible Monday output and cover rotated headers, spill dates, invalid input, sanitizer behavior, and live terminal restoration.
