Fix more TTY-dependent local CI tests

[computermode]

tryAgentCommitFastPath() only fires when hasTTY() is false.

This was resulting in local test failures for these tests.

@pfleidi and I were both running into these failures via mise test:ci

--- FAIL: TestTryAgentCommitFastPath_AcceptsSessionWithContent (0.01s)
    condense_skip_test.go:262:
                Error Trace:    /Users/pfleidi/entire/cli/cmd/entire/cli/strategy/condense_skip_test.go:262
                Error:          Should be true
                Test:           TestTryAgentCommitFastPath_AcceptsSessionWithContent
                Messages:       fast path should fire for session with content
    condense_skip_test.go:267:
                Error Trace:    /Users/pfleidi/entire/cli/cmd/entire/cli/strategy/condense_skip_test.go:267
                Error:          "test commit\n" does not contain "Entire-Checkpoint"
                Test:           TestTryAgentCommitFastPath_AcceptsSessionWithContent
                Messages:       should add trailer for session with content
--- FAIL: TestTryAgentCommitFastPath_SkipsEmptyButAcceptsContentSession (0.01s)
    condense_skip_test.go:294:
                Error Trace:    /Users/pfleidi/entire/cli/cmd/entire/cli/strategy/condense_skip_test.go:294
                Error:          Should be true
                Test:           TestTryAgentCommitFastPath_SkipsEmptyButAcceptsContentSession
                Messages:       fast path should fire for the content session
    condense_skip_test.go:298:
                Error Trace:    /Users/pfleidi/entire/cli/cmd/entire/cli/strategy/condense_skip_test.go:298
                Error:          "test commit\n" does not contain "Entire-Checkpoint"
                Test:           TestTryAgentCommitFastPath_SkipsEmptyButAcceptsContentSession
                Messages:       should add trailer from the content session

---

Note

Low Risk
Test-only change that sets ENTIRE_TEST_TTY=0 to make TTY detection deterministic and avoid hangs/failures in local CI; no production logic is modified.

Overview
Makes the tryAgentCommitFastPath regression tests deterministic by explicitly setting ENTIRE_TEST_TTY=0 so hasTTY() is forced false and the non-interactive fast path is exercised consistently.

This prevents local/CI runs from unexpectedly taking the TTY-dependent path and failing to add the Entire-Checkpoint trailer in condense_skip_test.go.

^{Reviewed by Cursor Bugbot for commit 700aace. Configure here.}

[Copilot]

Pull request overview

This PR fixes nondeterministic local failures in the tryAgentCommitFastPath() unit tests by making the tests explicitly simulate a non-TTY environment, matching the conditions under which the fast path is expected to run.

Changes:

• Force hasTTY() to return false in the relevant tests by setting ENTIRE_TEST_TTY=0.
• Stabilize expectations around whether the fast path fires and whether an Entire-Checkpoint trailer is added.