## Description
This PR changes guardian transcript compaction so oversized
conversations no longer collapse into a nearly empty placeholder.
Before this change, if the retained user history alone exceeded the
message budget, guardian would replace the entire transcript with
`<transcript omitted to preserve budget for planned action>`!
That meant approvals, especially network approvals, could lose the
recent tool call and tool result that explained what guardian was
actually reviewing. Now we keep a compact but usable transcript instead
of dropping it all.
### Before
```
The following is the Codex agent history whose request action you are assessing...
>>> TRANSCRIPT START
<transcript omitted to preserve budget for planned action>
>>> TRANSCRIPT END
Conversation transcript omitted due to size.
The Codex agent has requested the following action:
>>> APPROVAL REQUEST START
Retry reason:
Sandbox blocked outbound network access.
Assess the exact planned action below. Use read-only tool checks when local state matters.
Planned action JSON:
{
"tool": "network_access",
"target": "https://example.com:443",
"host": "example.com",
"protocol": "https",
"port": 443
}
>>> APPROVAL REQUEST END
```
### After
```
The following is the Codex agent history whose request action you are assessing...
>>> TRANSCRIPT START
[1] user: Please investigate why uploads to example.com are failing and retry if needed.
[8] user: If the request looks correct, go ahead and try again with network access.
[9] tool shell call: {"command":["curl","-X","POST","https://example.com/upload"],"cwd":"/repo"}
[10] tool shell result: sandbox blocked outbound network access
>>> TRANSCRIPT END
Some conversation entries were omitted.
The Codex agent has requested the following action:
>>> APPROVAL REQUEST START
Retry reason:
Sandbox blocked outbound network access.
Assess the exact planned action below. Use read-only tool checks when local state matters.
Planned action JSON:
{
"tool": "network_access",
"target": "https://example.com:443",
"host": "example.com",
"protocol": "https",
"port": 443
}
>>> APPROVAL REQUEST END
```
0b9e42f6f7