## Description
This PR trims `app-server-protocol`'s v1 surface down to the small set
of legacy types we still actually use.
Unfortunately, we can't delete all of them yet because:
- a few one-off v1 RPCs are still used by the Codex app
- a few of these app-server-protocol v1 types are actually imported by
core crates
This change deletes that unused RPC surface, keeps the remaining
compatibility types in place, and makes the crate root re-export only
the v1 structs that downstream crates still depend on.
## Why
The main goal here is to make the legacy protocol surface match reality.
Leaving a large pile of dead v1 structs in place makes it harder to tell
which compatibility paths are still intentional, and it keeps old
schema/types around even though nothing should be building against them
anymore.
This also gives us a cleaner boundary for future cleanup. Instead of
re-exporting all of `protocol::v1::*`, the crate now explicitly exposes
only the v1 types that are still live, which makes it much easier to see
what remains and delete more safely later.
## What changed
- Deleted the unused v1 RPC/request/response structs from
`app-server-protocol/src/protocol/v1.rs`.
- Kept the small set of v1 compatibility types that are still live,
including:
- `initialize`
- `getConversationSummary`
- `getAuthStatus`
- `gitDiffToRemote`
- legacy approval payloads
- config-related structs still used by downstream crates
- Replaced the blanket `pub use protocol::v1::*` export in
`app-server-protocol/src/lib.rs` with an explicit list of the remaining
supported v1 types.
- Regenerated the schema/type artifacts, which also updated the
`InitializeCapabilities` opt-out example to use `thread/started` instead
of the old `codex/event/session_configured` example.
## Validation
- `just write-app-server-schema`
- `cargo test -p codex-app-server-protocol`
## Follow-up
The next cleanup is to keep shrinking the remaining v1 compatibility
surface as callers migrate off it. Once the remaining consumers stop
importing these legacy types, we should be able to remove more of the v1
module and eventually stop exporting it from the crate root entirely.
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