Conversations on the new loop (M2.5, PR A)

- A top-level message that isn't a command is a conversation: an item in
  the `general` scope (L1), threaded under the operator's message, with
  `reply`, `ask_human` and `propose_work` and no workspace or execution.
  `general` is reserved as a project name.
- propose_work(project, title, summary) goes up as a revision for a
  go-ahead (or a plain yes). On go, under a file_issue intent (L8), the
  record issue is opened in that project, assigned to the agent and
  carrying the new item's ID; its item starts agreed, with the summary as
  its brief. Intake skips any issue carrying an ID (D1); boot adopts a
  filed issue or puts the proposal up again.
- A conversation closes after tuning.loop.general_idle_s (default a day);
  a reply in its thread then starts a new conversation that continues it.

Tests: conversation unit tests (threading, filing, the marker, an unknown
project, changes, idle close and continuation, a plain yes, both crash
cases, commands at top level); the walk with conversations, proposals and
idle time, and records_have_one_item / conversations_do_no_work; an e2e
conversation that becomes filed work.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

nisse-dev/tests/test_loop_milestones.py

@@ -60,11 +60,20 @@ class Forge:
         self.closed_issues: list[int] = []
         self.issues = [Issue(14, "Add count_words", "count words", "don", ())]
         self.deps: dict[int, list[int]] = {}  # issue -> the issues it depends on
+        self.assigned: list[int] = []  # issues the agent assigned to itself
 
     # intake
     def assigned_issues(self, repo: str, assignee: str) -> list[Issue]:
         return [i for i in self.issues if i.number not in self.closed_issues]
 
+    def create_issue(self, repo: str, title: str, body: str) -> int:
+        n = max([i.number for i in self.issues] + [0]) + 1
+        self.issues.append(Issue(n, title, body, "nisse-dev", ()))
+        return n
+
+    def assign_issue(self, repo: str, index: int, assignee: str) -> None:
+        self.assigned.append(index)
+
     def open_dependencies(self, repo: str, index: int) -> list[str]:
         return [
             f"{repo}#{n}"