Grants that outlive what they name, and a rule you can read

sharing.forget_principal has existed since shares did, documented as the thing
that stops a recycled id inheriting somebody's grant, and was called by nobody.
Deleting a group left every grant naming it; deleting an account left both the
grants to it and the grants of its own work -- that second half is the one
nothing else could catch, since their rows cascade and the shares of those rows
have nothing to cascade from. Both now run before the delete, while the rows are
still findable, and a deleted resource forgets its own.

library.share defaulted to False, which meant sharing shipped documented as done
and unreachable: the panel only renders for somebody holding it, so out of the
box nobody could share anything and nothing said why. It is on.

The panel itself was checkboxes inside the resource's *save form*, listing every
group and every account on the instance, unpaginated, on every detail page -- and
a tick only took effect if you also saved the resource. It is its own routes now:
search, one grant per POST, the panel re-rendered from what is stored. Anything
already shared stays listed whatever the search says, or removing a grant would
mean searching for the name it was given to.

Reports join the shareable set and memories still do not: a finished piece of
work is the thing somebody most wants to hand over, and a record about a person
is not content to pass round. reports.visible became sharing.visible_to, which is
the one line its own docstring predicted. Two things fell out: `owned` beside
`get`, because sharing grants reading and deleting is the owner's alone; and
reading somebody else's report no longer clears their unread dot.

Permissions gained the answer to "what can this person actually do?" --
explain() is resolve()'s working shown rather than thrown away, naming admin, the
baseline, or the groups that granted each one. That is the simulation the union
rule exists to make unnecessary, and until now the only way to get it was to open
every group and read the grids by eye. Users and groups are list-plus-detail, and
membership is edited from one side: it was on both, and a full-form POST from
either overwrote what the other had shown.

Read and write are split for notes, memory and skills -- checked on the tool's
declared risk, after the gate so it can only narrow, and defaulting on.

Quotas are the union rule applied to numbers, with the corner that makes it
interesting: zero means "no limit" and wins outright, or a group saying unlimited
would count for less than one saying a million. Absent means "no opinion".
_narrower folds a group's ceiling with the instance's and is deliberately not
min, for the same reason. Five axes, enforced where each is knowable -- before a
reply is built, before a second one starts, on an agent reply's clock, before a
minute of GPU, and beside the helper cap -- and usage is recorded even for a
reply that was stopped or errored, because an endpoint charges either way.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -20,7 +20,7 @@ lembas info                         # paths + counts, useful when confused
 lembas secret-key                   # generate LEMBAS_SECRET_KEY
 lembas create-admin                 # create or promote an admin
 
-pytest                              # 2024 tests, ~2min
+pytest                              # 2062 tests, ~2min
                                     # PLAN.md tracks what is and is not built
 ruff check .                        # lint (line length 100)
 python scripts/build_artwork.py     # regenerate artwork (SVG + PWA icons;
@@ -82,7 +82,9 @@ src/lembas/
     folders.py       folder CRUD
     admin.py         connections + instance settings
     admin_models.py  model ordering, defaults, images, access
-    admin_users.py   users, groups, permissions
+    admin_users.py   users, groups, permissions, quotas -- list plus detail,
+                     with "what can this person actually do?" answered
+    sharing.py       the share panel: search, and one grant per request
     admin_audio.py   speech-to-text and text-to-speech endpoints
     admin_search.py  web search provider and credentials
     admin_images.py  the ComfyUI, and the workflow templates on it
@@ -139,6 +141,8 @@ src/lembas/
     wake.py          starting a reply from outside a request -- one lock
                      discipline, shared by finished jobs and by schedules
     sharing.py       one visibility rule for every library store
+    usage.py         what an account spent this month, and whether it may spend
+                     more -- written even when the reply failed
     prompts.py       every injected prompt fragment, and {{variables}}
     metrics.py       tokens, context percentage and tokens/second
     tokens.py        the chars/4 estimate, for endpoints that report none
@@ -199,6 +203,10 @@ touching the code it names -- these are the same notes, not a summary.
   schedule something wrote a note and said it had).
 - `docs/notes/image-generation.md` -- the ComfyUI workflow with holes in it, what
   substitution walks, the review-and-retry loop, and how a failure reports itself.
+- `docs/notes/permissions-and-sharing.md` -- the union rule shown rather than
+  thrown away, where read and write are split and why not everywhere, quotas as
+  the union rule applied to numbers (and why zero wins), where each is enforced,
+  and the three deletes that have to forget a share because nothing cascades.
 - `docs/notes/search-and-extraction.md` -- extraction limits as a snapshot, why
   reciprocal rank fusion and not a weight, how a record scores as its best chunk,
   why vectors from two models never meet, and the session event that notices a