test(coderd): cover the turn tool policy at buildTurnEnvironment - #30867

…ilter (#30864)

Removes `allowedBehaviorToolNames`, `allToolNames`, and
`TestAllowedBehaviorToolNames`, and the active-name check they fed in
`appendDynamicTools`.

The check never skipped a tool. `appendDynamicTools` returns early for
Explore mode and plan mode, so at the check, `allowedBehaviorToolNames`
always returned every tool name. A dynamic tool that shares a built-in
tool's name is still dropped with a warning.

Validation: `go test ./coderd/x/chatd/ -run
'Dynamic|AllowedExplore|StopAfterPlan'` passes, and the pre-commit hook
(build, `lint/go`, `lint/go/new-code`) passed.

## Stack

This stack splits #28757, as requested in review. It moves the code that
prepares a chat turn into one file, `turn_environment.go`, and moves the
tool policy tests from full turns to a table test. chatd behaves as on
`main`, except for the debug log in #30865.

1. #30864 Remove the no-op `allowedBehaviorToolNames` filter
2. #30865 Log workspace agent lookup errors in turn preparation
3. #30866 Rename `prepareGeneration` to `buildTurnEnvironment`
4. #30867 Cover the turn tool policy at `buildTurnEnvironment`
5. #30868 Remove seven end-to-end tool policy tests
6. #30869 Name the `*Server` receiver `p` in `turn_environment.go`
7. #30870 Move the turn preparation helpers into `turn_environment.go`

> Xum, an AI agent, opened this PR for @ibetitsmike and wrote this
description.

…aration (#30865)

Logs the error from `getWorkspaceAgent` at debug level in turn
preparation. `prepareGeneration` discarded it.

The turn still goes on without the agent, as before. The agent only adds
its OS and working directory to the instruction header.

Validation: build and vet pass, and the pre-commit hook passed.

## Stack

This stack splits #28757, as requested in review. It moves the code that
prepares a chat turn into one file, `turn_environment.go`, and moves the
tool policy tests from full turns to a table test. chatd behaves as on
`main`, except for the debug log in #30865.

1. #30864 Remove the no-op `allowedBehaviorToolNames` filter
2. #30865 Log workspace agent lookup errors in turn preparation
3. #30866 Rename `prepareGeneration` to `buildTurnEnvironment`
4. #30867 Cover the turn tool policy at `buildTurnEnvironment`
5. #30868 Remove seven end-to-end tool policy tests
6. #30869 Name the `*Server` receiver `p` in `turn_environment.go`
7. #30870 Move the turn preparation helpers into `turn_environment.go`

> Xum, an AI agent, opened this PR for @ibetitsmike and wrote this
description.

Renames the turn preparation step after what it returns: the environment
for one turn. Only names change, plus one small change to how callers
release the environment.

- `generation_preparer.go` becomes `turn_environment.go`, and its test
file becomes `turn_environment_internal_test.go`. GitHub shows both as
renames. A comment in `compactionTriggers.test.ts` that names the test
file follows the rename.
- `prepareGeneration` becomes `buildTurnEnvironment`, and its result
type `generationPrepared` becomes `turnEnvironment`. Four
`TestPrepareGeneration*` tests become `TestBuildTurnEnvironment*`.
- The `Cleanup` field becomes the unexported `cleanup`, and callers use
`Close()`. `Close()` does nothing on a zero value.

The type stays in `generation.go` for now. #30870 moves it next to
`buildTurnEnvironment`.

Validation: build and vet pass, the renamed tests and the `toolinput`
tests pass, and the pre-commit hook passed.

## Stack

This stack splits #28757, as requested in review. It moves the code that
prepares a chat turn into one file, `turn_environment.go`, and moves the
tool policy tests from full turns to a table test. chatd behaves as on
`main`, except for the debug log in #30865.

1. #30864 Remove the no-op `allowedBehaviorToolNames` filter
2. #30865 Log workspace agent lookup errors in turn preparation
3. #30866 Rename `prepareGeneration` to `buildTurnEnvironment`
4. #30867 Cover the turn tool policy at `buildTurnEnvironment`
5. #30868 Remove seven end-to-end tool policy tests
6. #30869 Name the `*Server` receiver `p` in `turn_environment.go`
7. #30870 Move the turn preparation helpers into `turn_environment.go`

> Xum, an AI agent, opened this PR for @ibetitsmike and wrote this
description.