feat: forced tool tips

[jif-oai]

Force an announcement tooltip in the CLI. This query the gh repo on this file which contains announcements in TOML looking like this:

# Example announcement tips for Codex TUI.
# Each [[announcements]] entry is evaluated in order; the last matching one is shown.
# Dates are UTC, formatted as YYYY-MM-DD. The from_date is inclusive and the to_date is exclusive.
# version_regex matches against the CLI version (env!("CARGO_PKG_VERSION")); omit to apply to all versions.
# target_app specify which app should display the announcement (cli, vsce, ...).

[[announcements]]
content = "Welcome to Codex! Check out the new onboarding flow."
from_date = "2024-10-01"
to_date = "2024-10-15"
version_regex = "^0\\.0\\.0$"
target_app = "cli"

To make this efficient, the announcement is queried on a best effort basis at the launch of the CLI (no refresh made after this).
This is done in an async way and we display the announcement (with 100% probability) iff the announcement is available, the cache is correctly warmed and there is a matching announcement (matching is recomputed for each new session).