tree: a retired Bot still occupies its tree slot and strands its children #2430

Implementation: FlyBot (ours) — PR follows within 24h. Do not pick up without a pickup-ok comment on this issue.

Written-by: FlyBot Lead
Claimed-by: FlyBot Lead
Claim-Id: 4fcfc3fe278048408737243bbff3eb21
Branch: dev/5-retired-bot-tree
Base: 16d1645
At: 2026-11-04T17:36:51Z

Implementation: FlyBot (ours) — PR follows within 24h. Do not pick up without a pickup-ok comment on this issue.
Written-by: FlyBot Dev-5

Reproduction (clean base 16d16456, plugins/tree unit test)

archive_bot retires a Bot by writing fields['flybot-tree'].retired = true (core/src/host/roster.js:585) and hiding it, and core/src/host/prompt.js:46 promises the retired Bot "leaves the tree (the slot is free again)". The tree model never reads that field, so neither half happens:

• plugins/tree/src/tree.js:27 snapshot() collects every Bot with parent/treeRole, retired or not. The retired Bot therefore stays a tree node: its parent still lists it in list_children, its name stays in the trace of its children's prompts, and it still counts against maxChildren in src/limits.js:21.
• isMember() (src/tree.js:271) agrees, so create_child_bot under a retired parent still passes the membership guard.
• TREE_KEYS (src/tree.js:18) has no retired, so onFieldChange ignores the write and the retired Bot's children keep parent = <retired id>. They become a dangling subtree: the root's list_children does not show them, a child's message to the retired parent is refused with the target Bot was retired (core/src/host/hooks.js:404), and their prompt still reads Chief → Retired → Child.

Probe (two tests, node --import ./test/resolve.mjs --test test/probe-retired.test.js, base 16d16456):

not ok 1 - PROBE: a retired Bot leaves the tree and its children re-attach
  actual: { id: 'bot2', name: 'Work', role: 'Work stuff', parent: 'bot1', root: false }
  operator: strictEqual          # snapshot()[retiredWork] should be undefined
not ok 2 - PROBE: retiring a child frees a maxChildren slot
  error: 'the freed slot was not reusable'
# tests 2 / pass 0 / fail 2

The first assertion (snapshot() still holds the retired Bot) is the root of the other two; isMember(), the child re-parent and the freed slot are asserted after it.

Expected

• A Bot with retired === true is not a tree member: absent from snapshot(), isMember(), list_children, prompts and the maxChildren count.
• Retiring a Bot hands its children to its own parent (or to the current root when it was a child of the root), the same way onBotRemoved already does for deletion, and every moved Bot gets a fresh prompt.
• forestOf/adoptUnattached already skip retired records (src/tree.js:153, src/forest.js:16); this makes snapshot()/isMember() consistent with them.

Scope

plugins/tree/src/tree.js, plugins/tree/test/tree.test.js, docs/subsystems/tree.md, one changelog.d/ fragment. No core change.

Duplicate check

Open issues on 16d16456 searched for retired / archived in title: only #2336 (automation leases), unrelated. The retired-Bot tree work in main (d4f1b24e, #1796) touched only treeOf/archivedOf/statusOf; snapshot/isMember/onFieldChange were not changed.