docs(agents): trim the always-loaded contract from 569 to 472 lines

[IanQiu979]

Why

AGENTS.md is firstmate's always-loaded contract: every session of every fleet member pays its token cost on every turn, whether or not that session ever hits the situation a given line describes. It has grown to 569 lines, largely by accumulating conditional and reference detail inline instead of routing it to the owner that already documents it - exactly the failure mode firstmate-coding-guidelines exists to prevent.

This applies that skill's knowledge-placement decision tree and one-owner rule to the current file, taking it to 472 lines. It is the same restructure as 039747a (483 -> 393), redone against current main.

039747a never reached this repo. It sat unpushed on a local main that was 163 commits behind origin/main, and because /updatefirstmate is fast-forward-only, that one local commit silently blocked every self-update for 25 days. Landing the restructure here is what ends that.

What this is not

Documentation only. No behavior, contract, capability, or rule substance changes. No script, test, or workflow is touched, and CLAUDE.md remains the canonical @AGENTS.md pointer file.

There was deliberately no target line count. Nothing was cut to hit a number - only content with a verified owner elsewhere was routed, and the verification for each removal is recorded in the commit body.

What moved

• Section 2 - the 78-line annotated state//config//data/ tree became a compact top-level map plus pointers. docs/configuration.md's "Operational home layout and state" section states outright that it is the single owner of the top-level layout and that producer script headers own exact child-file fields; every removed entry was traced to it, to CONTRIBUTING.md/README.md (metadata.internal), or to a named producing script (fm-check-register, fm-pr-poll, fm-pr-check-migrate, fm-classify-lib, fm-decision-hold, fm-procevent, fm-startup-network, fm-wake-lib, fm-pending-reply-lib, fm-spawn, fm-teardown) before removal.
• Section 3 - the step-by-step mechanism narrative and its positional ordering phrases, which bin/fm-session-start.sh's header already owns as this very section states in its first sentence.
• Section 4 - the quota-array selection procedure, routed to quota-array-dispatch, which declares itself its single owner.
• Sections 1, 3-11, 13 - adjacent single-purpose sentences joined into one sentence each. Clause joins only; no substance dropped.

What deliberately did not move: section 9's rewrite table

039747a's consolidate-adjacent-sentences method would merge section 9's 11-row rewrite table into prose, and it did exactly that. This PR deliberately does not, and the deviation is the point.

That table is a lookup surface, not prose. An agent consults it mid-response, one term at a time, while rewriting an internal label out of a captain-facing message - not once at session start like the rest of the file. An agent scanning for a single term needs rows; compressing a lookup table into a semicolon-chained sentence optimises the wrong thing. Ten lines is cheap insurance against leaking internal jargon to the captain, a rule enforced on every message all session long.

039747a's method is right for prose and wrong for a table. Please do not re-merge it.

That reasoning is now recorded in AGENTS.md's own ## Maintaining this file section rather than only here, so it travels with the file and lands in front of whoever next runs a consolidation pass over it.

Restoring the table also restored the "do not expose" sentence above it verbatim. The merged draft had quietly added adapter to that prohibition list - a new rule, which a documentation-only restructure must not introduce, by the same reasoning that governs the two restorations below.

What was deliberately kept, not dropped

Three facts had no other owner. Removing them would have been a real loss, so they stayed inline:

1. The never touch watcher / Claude and Cursor turn-end / sub-supervisor / wake-recovery internals class, kept as one sentence worded to be exactly as strict as the per-entry lines it replaces and no stricter. Delete-safety for every other state/ record now routes to that record's producing script rather than being asserted either way, so no permission was silently removed.
2. Registered process-to-event sources keep supervision required even with no fleet work. This only ever appeared in the section 2 map; it moved to section 8, its real owner, beside the identical Relay rule.
3. The watcher's custom-check execution boundary - only trusted repository scripts and hash-validated registered checks execute, and every other state check is rejected without running - which is documented nowhere else. It was folded into section 7's existing fm-check-register.sh rule, at its actionable point.

Section 4's hard "never"s were preserved inline for the same reason: never infer a credential store, provider family, or quota mapping from a name; never launch another harness's CLI to judge a candidate; missing evidence is disclosed uncertainty, never a credential or login escalation; only concrete contradictory evidence blocks. quota-array-dispatch itself names AGENTS.md section 4 as the owner of five things - intake boundary, load trigger, malformed-config refusal, every-candidate accounting, and the strongest-reasoning/tie rules - and all five remain inline.

Two substance changes the review caught, both reverted

The gate's review flagged two places where a "prose tightening" had quietly changed the contract. Both were put back:

1. Relay may require had become Relay ... require. A modal verb is substance: may require is a permission, require is an obligation. It reads back exactly as before, and the process-to-event fact that moved here from section 2 keeps its own original strength rather than the two sharing one flattened verb.
2. The bootstrap detect-only checks lost their always run guarantee. That clause is the contrast with the very next sentence's mutating sweeps, which run only under the lock; without it a session could infer that a lock-refused start skips detection entirely. Restored.

Both are the same class of error: a restructure that must not change substance had changed it in prose that looked like condensation.

Safety inventory

The commit body carries a section-by-section inventory naming every hard rule, refusal condition, fail-closed behaviour, and skill trigger and marking it PRESENT, in the same shape as 039747a's. If an item could not honestly be marked PRESENT, something was removed that needed putting back.

Relationship to #2520

#2520 is open against this same file and adds a two-sentence note that the directory map is a navigational excerpt rather than an inventory, and that an absent entry never proves a state/ file is foreign or safe to remove. That note is directly load-bearing for this restructure, so it is reproduced verbatim here rather than left to a rebase conflict where it could be lost. None of #2520's other seven fixes are touched.

Merge-order caution: because both branches add that same note, whichever lands second needs a quick check that it ends up present exactly once - not duplicated, not dropped. Everything else in the two branches is disjoint.

Verification

• bin/fm-doc-audience-check.sh passes (surfaces=68 local_links=251).
• No section was renumbered, so every AGENTS.md section N cross-reference from docs/, .agents/skills/, CONTRIBUTING.md, README.md, and bin/ script headers still resolves. Each was checked, and each referenced rule still exists.
• CLAUDE.md is unchanged and still the canonical @AGENTS.md pointer file, not a symlink.
• AGENTS.md is the only changed file across all three commits.
• The full no-mistakes pipeline passed on this branch: review, test, document, and lint all clean. Push/PR/CI ran outside it because this repo is pull-only for the author, so the branch is delivered from a fork.

Commits

1. The restructure itself.
2. Three restorations after review: the may require modality, the always run guarantee, and section 9's bulleted table.
3. The one-line note in ## Maintaining this file recording why that table stays a list.