Fix review findings: resolver safety, command contract, docs

[AngelMsger]

Addresses the code review of v0.2.0. All 5 findings were verified against the
code and fixed. #2/#3/#4 change the CLI's external contract — the next
release should be v0.3.0.

#1 — Security: ID resolver mis-resolution (high)

resolveID only ever extracted a page ID; passing a comment/attachment URL
resolved to the page ID, so comment delete <page-url> could delete the whole
page. Fixed:

• urlref now extracts focusedCommentId from comment permalinks.
• resolveID is split into resolvePageID / resolveCommentID /
  resolveAttachmentID. A plain page URL given to a comment/attachment command
  is rejected instead of silently acting on the page.

#2 — --format flag conflict

The body-format flag on page create/update and comment add/update is
renamed --format → --body-format; it no longer shadows the global
--format (json/table/ndjson) output flag.

#3 — Non-JSON success output

config path/use-context/delete-context/init, auth login/logout and
skill install/uninstall/path now emit JSON via s.emit. Interactive
prompts moved to stderr; stdout is uniformly JSON (version stays plain text by
design, matching the --version flag).

#4 — Pagination

List commands now emit a {items, next, has_more} envelope and accept
--cursor, so an agent can page deterministically. output table/ndjson
rendering and --fields projection are envelope-aware.

#5 — Stale docs

docs/technical-design.md, README.md and the embedded Skill updated to the
implemented surface; the error model documents conflict / exit 11.

Verification

• gofmt / go vet / go test ./... green; make e2e 44/44.
• New tests: urlref focusedCommentId; resolver-safety (page URL rejected);
  list-envelope rendering/projection (output); envelope + safety CLI tests.
• make docs regenerated; generator idempotent.
• Manual smoke: page create --help shows both --body-format and global
  --format; comment delete <page-url> errors COMMENT_URL_NO_ID.

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