Sync API docs from bc3: example fixes and join-a-project wording

[jorgemanrubia]

This syncs bc3's doc/api/ at master 2ee862e469 to bump the mirror. It carries two things and nothing else: no other team's unsynced doc changes show up in the copy.

• Fixes Copilot found on Sync API docs from bc3 #446 (bc3#13388):
  • card_table_templates.md and template_library.md now show the response before the cURL, and the copy example uses the same id in its request and response.
  • event_feed.md: its three HTTP response examples now have route markers.
  • timeline.md: performed_by is Agent, or Tombstone once the agent is deleted.
• Later wording for Join a project (bc3#13389), following Document joining an all-access project (POST /buckets/:id/admissions.json) #437:
  • people.md now says "has access to" instead of "has joined".
  • Only a token acting as the agent itself gets 403.
  • "Update who can access a project" manages the people you name.

After this, sections/ and README.md match bc3 doc/api/ exactly.

Synced from bc3 doc/api/ by script/api/sync_to_bc3_api — not a hand-edit.

[Copilot]

🟢 Approved

The synchronized documentation changes are consistent, correctly marked, and match the stated scope.

Pull request overview

Syncs authoritative bc3 API documentation updates into this mirror.

Changes:

• Aligns template request/response examples and ordering.
• Adds missing event-feed route markers.
• Clarifies project access and deleted-agent behavior.

[!TIP]
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File summaries

File	Description
sections/card_table_templates.md	Corrects example ordering and identifiers.
sections/event_feed.md	Adds response route markers.
sections/people.md	Clarifies project access and agent-token behavior.
sections/template_library.md	Aligns names, ordering, and copy IDs.
sections/timeline.md	Documents tombstones for deleted agents.

Review details

• Files reviewed: 5/5 changed files
• Comments generated: 0
• Review effort level: Balanced

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