docs: name the conflict watchpr will never report

AGENTS.md

@@ -224,18 +224,27 @@ wrapped per stage (login / read denied / write denied) via `ErrVaultDenied`.
   read, so a PR that is already conflicted or already CI-failing when watching
   starts is polled on rather than reported. That suppression is printed with the
   baseline, since a silent watcher and a watcher with nothing to say look alike.
+  The baseline goes to stderr in both modes — a JSON record under `--json` —
+  because automation is what most needs it and stdout carries the result.
 - Mergeability is the one `watchpr` rule needing a run of observations
   (`prWatch`). Gitea 1.26 sends `mergeable` as a plain bool — always present,
   never null — and sends `false` both for a real conflict and while it recomputes
   the merge base after a push, which is exactly when an agent starts a watch. So
   `false` counts only once this watch has seen a merge computation start (the PR
-  was mergeable, or `head.sha`/`base.sha` moved), and then only across two
-  consecutive polls of an unchanged head and base; a mergeable poll, an unknown
-  one or a failed poll all break the run. `base.sha` is the base branch tip as of
-  the response, not the merge base at PR creation, so it moves when main does.
-  `Mergeability` stays tri-state for what the bool cannot carry: an absent/null
-  flag from some other Gitea, and a state no successful poll ever filled in.
-  Head and base SHAs are read only to arm this rule — a push never alerts.
+  was mergeable, or `head.sha`/`base.sha` moved), and then only once the run of
+  `false`s has spanned `conflictWindow` (2m); a mergeable poll, an unknown one or
+  a failed poll all break the run. The debounce is wall-clock, measured from the
+  tick that fired each poll, because what it outlasts is the recompute and
+  `--interval` spans seconds to hours. Arming and the run are independent:
+  movement arms and nothing else, since `base.sha` is the base branch tip as of
+  the response, so it moves for every open PR whenever main does and a run reset
+  there could never complete on a busy repo. `Mergeability` stays tri-state for
+  what the bool cannot carry: an absent/null flag from some other Gitea, and a
+  state no successful poll ever filled in. Head and base SHAs are read only to
+  arm — a push never alerts. The residue: a conflict landed by the push just
+  before the watch began, on a head and base that never move again, is never
+  reported; Gitea's payload has no field separating it from a check in flight
+  (`merge_base` is the true merge base and does not move on recheck).
 - CI "combined status" comes from `/commits/{sha}/status`; an empty head SHA
   yields an empty state without an API call.
 - Gitea backs every PR with an issue of the same number and serves comments from

README.md

@@ -88,13 +88,21 @@ gets a **new comment from someone other than the agent**, its **CI fails**
 transitions — CI `pending`→`success`, the agent's own comments and pushes — are
 ignored, and so is any condition the PR was already in at the baseline: a PR
 that is already conflicted or already failing when watching starts keeps being
-watched, and the baseline line says which conditions it is staying silent about.
+watched, and the baseline line — written to stderr, as a JSON record under
+`--json` — says which conditions it is staying silent about.
 
 Gitea reports `mergeable: false` both for a real conflict and while it
 recomputes the merge base after a push, so a conflict is only reported once the
-watch has seen a merge computation start — the PR was mergeable, or its head or
-base commit moved — and then only across two consecutive polls of an unchanged
-head and base.
+watch has seen a merge computation start (the PR was mergeable, or its head or
+base commit moved) **and** the non-mergeable polls have then run unbroken for
+two minutes. The debounce is a duration, not a poll count, because what it has
+to outlast is Gitea's recompute and `--interval` ranges from seconds to hours.
+
+One case is therefore never reported: a conflict introduced by the push
+immediately before the watch started, on a PR whose head and base never move
+again. Nothing in Gitea's payload separates that from a merge check still in
+flight, so watchpr stays silent about it for as long as it runs — the baseline
+line is how you see it.
 
 ```bash
 # Watch until something meaningful happens (default interval 60s)