kb: a pipe discards the exit code you meant to read

Fourth occurrence in one campaign, and this one was in a tool I wrote TO BE
the reliable answer. scripts/pr-reviews --wait correctly exited 1 on a
timeout, and my invocation ended in '| tail -20; echo', so the harness
reported 0 — a review window that had EXPIRED read as a review that had
ARRIVED, which is the dangerous direction.

The earlier three: pr-watch reading tr's status through a pipe; a probe
reporting EXIT=0 from a checker that had exited 1; and PIPESTATUS in zsh,
where the array is lowercase pipestatus — the two shells differ, which is its
own trap.

The script's usage now says not to pipe it.

Closes improvise-711n (,.2f yielded zero decimals — the spelling our own docs
show) and improvise-x1ns (the preflight undercount ChatGPT Codex found on a
PR I had already merged unread).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FC2jVn8Au7E9JPkw6bwXXH

prolog-sessions/kb.pl

@@ -299,6 +299,7 @@ doctrine(cfg_test_and_pub_crate_are_different_walls,'A visibility plan written f
 doctrine(cargo_tree_shows_dev_edges_by_default,'Asking whether a feature leaked a dependency into a shipped build, a plain cargo tree -p improvise-protocol --target wasm32-unknown-unknown reports serde_json PRESENT -- because the default output includes dev edges. --edges normal is what answers the question, and it reports 0. Verified both ways by the orchestrator. Same class as grep_over_git_diff_is_silently_empty_under_an_external_differ: a command that looks like it answers the question, answering a neighbouring one, in the direction that reads as a finding rather than as a pass. A feature that adds a dependency to a wasm bundle crate must be checked with --edges normal, and per-crate, because the CI wasm job checks each crate separately and feature unification cannot reach across that.').
 doctrine(an_unreachability_claim_is_only_as_wide_as_the_routes_enumerated,'PR #98 predicted the composition-time mode drift itself and declared it unreachable BECAUSE the toggle route (R) is a stranding decline in the browser. True of that route. A VIEW SWITCH reached the same drift, because records-ness is auto-detected from the axes, so a switch changes it with nothing in the batch saying \"records\" -- found by ChatGPT Codex. The ENUMERATION of routes is the part nothing checks, so an unreachability argument is evidence about the routes you thought of and about nothing else. Same shape as a_mitigation_that_names_the_wrong_file_is_not_a_mitigation. The remedy is to close the CLASS by observation rather than to patch the route.').
 doctrine(a_precondition_derived_from_its_own_expectation_guards_nothing,'A loop test whose precondition is computed from the same tuple element as the assertion cannot be relaxed one iteration at a time: relaxing the assertion relaxes the guard too, and the test then fails for the wrong reason -- which reads exactly like the bug. Assert the two as SEPARATE facts. Corollary for check_the_checker over a loop: an injection that stops the loop at iteration 1 leaves every later iteration untested, so each direction must be reached deliberately. Found by the PR #98 author in its own bidirectional test while proving the second direction.').
+doctrine(a_pipe_discards_the_exit_code_you_meant_to_read,'FOURTH occurrence in one campaign, and the last one was in a tool written TO BE the reliable answer. scripts/pr-watch once read tr exit status through a pipe. An orchestrator probe reported EXIT=0 from a checker that had exited 1, because the pipeline ended in tail. Another read PIPESTATUS in zsh, where the array is lowercase pipestatus. And scripts/pr-reviews --wait correctly exited 1 on a timeout while the invocation \`... | tail -20; echo\` reported 0 -- so a review window that had EXPIRED read as a review that had ARRIVED, which is the dangerous direction. In bash and zsh the exit status of a pipeline is the LAST command, so any \`cmd | head\`, \`| tail\`, \`| grep\` discards it. Redirect to a file and read the file, or check PIPESTATUS[0] in bash / pipestatus[1] in zsh -- and note the two shells differ, which is its own trap. A gate whose status you sampled through a pipe has told you about the pager.').
 work_done('improvise-8tk',bug_fix,'ZZ/:wq quit even when the save failed, silently discarding the model. Save now aborts the effect batch on failure; save_to_current_path/1 returns Result<String,String>; three tests in ui/effect.rs.').
 work_done('improvise-907',bug_fix,'Import wizard step machine redesign: validation_error() gate at ReviewProposals (no-category and over-limit), history-stack previous() bound to Left on every step, and Done made a real confirmation step holding the built workbook. Superseded improvise-gfq, improvise-o1c, improvise-c6j.').
 work_done('improvise-6sq',wont_do,'Merging EditOrDrill and EnterEditAtCursorCmd into one EnterEdit{mode} is not safe: they differ in WHEN the cell value is read, not in a mode parameter. Added ui/app.rs::tests::i_and_o_diverge_on_an_empty_records_grid as executable evidence.').