docs(plan): set the V0.6 release milestone and record the merge of #27 to #31 (plan r19) - #33

…erge of #33 to #36 (plan r20) (#38)

* docs(plan): record the MCP direction, the blank-session fix and the merge of #33 to #36 (plan r20)

The owner came back on 2026-10-23 with two problems in Zed: the MCP notice at the start
of each new thread, and a thread without a message that cannot be opened after Zed
restarts. The owner chose an optional extension package for MCP (core, harness and CLI
stay without an MCP client) and asked for the blank-session fix as a PR at once. On
2026-10-25 the owner asked for the release content first, then for the merge of #33 to
#36.

The merge is done. #33 with `gh pr merge --squash` (ca2ab85). #34 to #36 with
`gh stack link 34 35 36` (stack #37) and `gh stack merge 37 --yes --squash` (fa4887b,
34c11d9, e0f2a36). The tree of each commit is the tree of its PR head plus the two plan
files of #33. CI and TUI CI pass on e0f2a36 (pytest 2,908 passed on Python 3.11, 3.12
and 3.13; nextest 8,490 passed, 0 failed, 22 skipped).

PLAN-RUST-AGENT-RUNTIME-REMOVAL.md:
- Decision 17 gets a correction (#34: session/load and session/resume open an empty
  session for a canonical UUID that has no file).
- New decisions: 19 (the MCP direction, decided), 20 (the versions of the extension
  packages and their core floors), 21 (the 11 defaults of the MCP design).
- V0.6: 14 commits, one more package. Conditions 1, 3, 5 and 6 and the known issues are
  rewritten.
- r19 said the three extension packages stay as they are. That is wrong. The packaging
  test requires that each floor equals the workspace version, so a core of 0.6.0 needs
  `>=0.6.0` in all four extension packages (checked: 4 tests fail). This is decision 20.
- The status, section 7, appendix A.1 and A.2, the index and the revision log carry the
  same facts.

The execution log gets section 10.23: the cause of both problems, the three PRs, the
release content, the merge, the check of the trees, CI on main, the floors, and what is
not verified.

docs/TUI-AND-CODE-AGENT.md: the paragraph about MCP servers now says that `pi-mcp-py`
connects them and what the agent says without it.

No condition of V0.6 is met yet. Only documents change.

* docs(plan): record the answer of the owner to decisions 20 and 21 (plan r20)

The owner answered "follow your lean" for the two open decisions of r20.

Decision 20 (versions and core floors of the extension packages): option (a). At the
version bump (V0.6 condition 5) the four extension packages get the core floor
`>=0.6.0`. pi-web-access-py, pi-goal-x-py and pi-dynamic-workflows-py go from 0.2.0 to
0.3.0, as V0.5 did in 7e7d4d4 (0.1.0 to 0.2.0). pi-mcp-py stays at 0.1.0 (first upload).
The lean did not say which digit to raise. 0.3.0 is my choice from the V0.5 precedent;
the plan and the execution log say so.

Decision 21 (the 11 defaults of the MCP design): all defaults stay, including Q3
(annotations are trusted) and Q5 (no way to configure servers in zypi). No code change.

Neither decision changes code. The change of decision 20 belongs to the PR of
condition 5, which is not open yet.

Files: the plan (status, V0.6 section, next steps, decisions 20 and 21, the lists of the
decision section, index, revision log, one link definition), the execution log (section
10.23 and its revision-log entry), the MCP design (section 10: one sentence). Only
documents change.