Backlog: O5 done 2cc29048b84a

- [x] O10a Heads at scale (first part of O10): `State::maximal` compared every pair of heads (quadratic; about 1.5 s per call at 4 500 heads, called three times per commit); now one walk. Commit reuses the snapshot's base state instead of loading it again.

- [x] O10b Parallel snapshot work: rendering the base state's files, building file graphs from a checkpoint, and reading working-copy files now run on every core (rayon).

- [ ] O10c Snapshot without the whole base (rest of O10): load only the file graphs a snapshot needs (a checkpoint split per file or indexed), skip reading and rendering files whose stat matches a manifest written for the same base, cache materialized states. Needs a spec change to the checkpoint format; target spec §25.

- [ ] O6 Error messages audit: every user-facing error says what to do next; `oxy doctor` checks identity, config, remotes, CA files, hub reachability.

- [ ] O7 Shell completions (`oxy completions bash|zsh|fish`) and man pages generated from clap.

- [ ] O8 Git round trip on real history: import a scratch mirror of tetriblox (never the live repo), export it back, compare trees at every commit.

- 2026-09-28 V3 done: oxygenhub-vscode 0.4.0: `#` and `@` completion in the Oxygen commit box and comment editors, hover on `#N`; repository from the SCM root. Parsing tested in Node (pass 10, fail 0). Installed in both profiles.

- 2026-09-28 O10b done: rayon for materialize, checkpoint file graphs and working-copy reads. At 10 000 files: clean status about 800 to 460-580 ms, commit 861 to 550-605 ms. Remaining cost is loading the whole base (O10c, needs a checkpoint format change in the spec, so left for Andy to agree). Hub redeployed.

- 2026-09-28 H4 done: `/{owner}` profile (identicon, display name, bio, location, website, keys, organisations, visible repositories, activity by that person; never the email) and organisation page (description, members and roles, teams with sizes, repositories, activity); `/avatar/{name}` identicons also in the header and feeds; migration 0008 (bio, website, location) and Settings fields (http(s) websites only); `avatar` and `help` reserved. Test `profile_and_organisation_pages`; screenshot checked; deployed (andymccall profile 200 on Earth).