docs: map the two prompt implementations behind the OD Next fork (#7649)

* docs: map the two prompt implementations behind the OD Next fork

`composeSystemPrompt` returns early for OD Next runs, so the legacy stack below that return — the designer charter, the discovery layer, and the deck framework directive that embeds deck protocol v1 — never reaches those runs. Nothing in the repository said so, and prompt changes have been landing on one side only. The deck case is live: the OD Next `ppt.md` pins none of `data-od-deck-protocol`, the `od:deck-ready` announce, the `od:slide-state` posts, the `od:slide` listener, `id="deck-stage"`, or the print stylesheet, so a deck generated on that path can fail to be recognized as a v1 deck, paged from the host toolbar, or exported to PDF. Eligibility is re-evaluated per run and can latch down mid-session, which is why the divergence shows up as an intermittent bug.

Adds `apps/daemon/src/prompts/AGENTS.md` (fork point, the four variant axes, and a host runtime contract table naming which side carries each contract today) and `plugins/_official/scenarios/od-next-strategy/AGENTS.md` (asset roster and package-hash rules, and why maintenance notes must stay out of `assets/`, which is sent to the model verbatim). Root AGENTS.md gains an index entry and a Prompt variants section. Pointers go at the two fork sites, both deck-framework copies, and the OD Next atom registry, which is itself declared twice.

Documentation and comments only; no prompt bytes change. Validated with pnpm typecheck, pnpm guard, the daemon prompt suites (207 tests), and the contracts system-prompt / web-clone / deck-protocol suites (28 tests).

* docs: add PR #7568 as the worked example of a one-sided prompt change

The variant map says the two sides exist; it did not show what missing one costs a careful author. #7568 (merged 2026-08-29, `973e868ce`) is the case: it introduced deck protocol v1 across 18 files, handled the daemon/contracts prompt-copy split completely — shared constant, both copies changed, a guard added on each side — ran the full web and contracts suites plus two packaged DMG end-to-end runs, and touched nothing under `plugins/_official/scenarios/`. Its own stated goal was to stop new navigation dialects appearing; the OD Next path kept generating decks with no protocol at all, reported two days after merge.

Records the three reasons the miss stayed invisible, each still true today: both guards it added call `composeSystemPrompt` without an OD Next recipe so they cannot pass the fork (one is named 'ships new Agent decks with OD Deck Protocol v1' and is green), the prompt matrix snapshot updated cleanly because every scenario in it takes the legacy branch, and sharing a constant fixed only the machine-readable half — the surrounding directive prose had already drifted between the two copies before #7568 and still differs on main.

Documentation only. Validated with pnpm guard in a worktree on this branch.

* docs: mark the deck fork at the sites an agent actually edits

The file-top and fork-point pointers only reach an agent that reads from line 1. The edit an agent actually makes for a deck rule lands in the middle of DECK_FRAMEWORK_DIRECTIVE (368 lines below the daemon file's header) or at the push site (446 lines below the fork), typically reached by grepping and reading a short span — where no pointer was in view. Put a two-line marker at each of those four sites instead: above DECK_FRAMEWORK_DIRECTIVE in both prompt copies, and above the deck/freeform push guard in both, which covers both push branches. Line references in the two AGENTS.md files are re-pinned for the shift.

Comments only, placed outside every template literal. Verified byte-identical prompt output against origin/main: 8 scenarios x both composition paths, sha256 and length compared in one worktree with the source files swapped and contracts rebuilt — all 16 pairs identical. pnpm typecheck, pnpm guard, daemon tests/prompts (207), contracts system-prompt / web-clone / deck-protocol (28).

* docs: move the prompt variant map to docs/ and refresh it for #7651

Two changes in one, because main invalidated the old shape while it sat in review. Structural: the guidance moves from two nested AGENTS.md files to one `docs/prompt-composition.md`, matching how the root index already carries `docs/architecture.md` and `docs/skills-protocol.md`. Nested AGENTS.md is not auto-loaded on file access, so proximity bought no delivery that the root pointer and the in-file markers do not already provide. The plugin folder keeps a short AGENTS.md for the one rule that is only meaningful there — never write maintenance notes into `assets/`, which reaches the model verbatim. Naming it after the structure rather than the experiment keeps it valid if OD Next is retired or graduates: two of the four axes are independent of it.

Factual: #7651 closed the deck gap this document reported, by collapsing the scaffold to one source in contracts and reaching OD Next through `resolveOdNextDeckFrameworkMode` rather than the markdown assets. The contract table's deck rows now read supported on both sides, the daemon deck-framework file is a re-export, and the two markers that claimed OD Next never receives the directive are removed rather than reworded. #7568 and #7651 are now presented as a pair — a one-sided change and the follow-up nearly twice its size that repaid it. Remaining gaps are recorded: five daemon/contracts prompt pairs still hand-maintained, and `core-slim.ts` absent on the contracts side.

Documentation and comments only. Prompt output verified byte-identical against the merge base: 8 scenarios x both composition paths, sha256 and length, markers reverted and reapplied in place. pnpm typecheck (0 errors), pnpm guard, daemon tests/prompts (210), contracts system-prompt / web-clone / deck-protocol / od-next-prompt-recipe (53).

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Co-authored-by: Cheems <94773058+itscheems@users.noreply.github.com>

plugins/_official/scenarios/od-next-strategy/AGENTS.md

@@ -0,0 +1,15 @@
+# `od-next-strategy` (OD Next V2 prompt assets)
+
+Everything under `assets/` is sent to the model **verbatim** as part of the
+prompt bundle. Never write repository-maintenance notes, TODOs, or
+cross-references into those files — they reach the model as instructions.
+Maintenance notes belong here instead: this file is not part of the asset
+roster (`apps/daemon/src/plugins/strategy-package.ts:158`), so it is never read
+or hashed at runtime.
+
+This folder is one half of a two-sided prompt implementation, and not all of OD
+Next's content lives here — host runtime contracts such as the deck framework
+are carried in TypeScript, not in these task profiles. Before changing anything
+here, read [`docs/prompt-composition.md`](../../../../docs/prompt-composition.md):
+the fork point, the variant axes, the host contract table, the asset roster and
+package-hash rules, and the known gaps.