feat(voyage): S18 — framing-hardening (min-version gate + memory status + pre-2.2 doc + flagship hedge)

Closes devils-advocate audit #4–#6 (MAJOR×MED). Four additive, non-breaking
changes to the v5.5 framing-alignment machinery:

1. --min-brief-version <ver> gate (audit #4). Opt-in version floor on
   /trekplan + /trekresearch, forwarded to brief-validator as --min-version.
   New opts.minBriefVersion warns BRIEF_VERSION_BELOW_MINIMUM (never blocks)
   when a brief declares a version below the floor; trekreview exempt; absent
   opt = no check. CLI shim parses --min-version and skips its value token in
   filePath detection.

2. memory_alignment.status field (audit #5). brief-reviewer now emits
   status: verified | n_a | contradictions so a score-5 N/A (no memory) is
   distinguishable from a score-5 verified-aligned brief — the score≥4 gate
   passes in both, status reveals whether the wrong-premise defense ran.

3. Document pre-2.2 = zero framing enforcement (audit #4). HANDOVER-CONTRACTS
   §Handover 1 now states the producer-elective hole + two remedies. Also
   fixes a stale "current is 2.1" line (current is 2.2).

4. Soften flagship overselling (audit #6). CLAUDE.md Context-Engineering
   principle now hedges that main-context relief is asserted-by-design, not
   measured (T1 PoC found Δ≈0); README carried no false claim to fix.

TDD: 8 new tests written failing-first (5 validator, 1 trekbrief status pin,
2 doc-consistency cross-file pins). Suite 691→699 (697 pass / 2 skip / 0 fail).
No flagship prose-pin added (deliberate, per S19 anti-bloat).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LqBYc8Ltrk7LipyJmGxXiB

docs/HANDOVER-CONTRACTS.md

@@ -96,10 +96,12 @@ Optional but standard sections: `## Non-Goals`, `## Constraints`, `## Preference
 
 **State machine** detail: a brief that says it has research topics but skipped them must explicitly admit it (via `brief_quality: partial`). This is the most common failure mode the validator catches.
 
-**Versioning:** current is `2.1` (v5.1 — adds optional `phase_signals` + `phase_signals_partial`). The forward-compat policy in `brief-validator.mjs` header still applies: unknown frontmatter keys flow through silently, so a `2.1` brief still validates against pre-v5.1 consumers. The version bump exists because v2.1 activates the **version-conditional sequencing gate** (above) — the only check in the validator that triggers on `brief_version` rather than field-presence. There are no live `1.x` briefs; remove legacy paths in next major. The v5.5.0 contract formalization **established `2.1` as the public-contract baseline** (see the PUBLIC CONTRACT callout under the Handover 1 heading): per the S3 effort-axis decision, `phase_signals` stays **optional**, and the v2.1 sequencing gate (`phase_signals` **or** `phase_signals_partial`) is the stability mechanism. Promoting `phase_signals` to required would be a future breaking change under the protocol above — explicitly *not* part of the v5.5.0 formalization.
+**Versioning:** the `2.1` schema axis (v5.1 — adds optional `phase_signals` + `phase_signals_partial`; current is `2.2`, see the next paragraph). The forward-compat policy in `brief-validator.mjs` header still applies: unknown frontmatter keys flow through silently, so a `2.1` brief still validates against pre-v5.1 consumers. The version bump exists because v2.1 activates the **version-conditional sequencing gate** (above) — the only check in the validator that triggers on `brief_version` rather than field-presence. There are no live `1.x` briefs; remove legacy paths in next major. The v5.5.0 contract formalization **established `2.1` as the public-contract baseline** (see the PUBLIC CONTRACT callout under the Handover 1 heading): per the S3 effort-axis decision, `phase_signals` stays **optional**, and the v2.1 sequencing gate (`phase_signals` **or** `phase_signals_partial`) is the stability mechanism. Promoting `phase_signals` to required would be a future breaking change under the protocol above — explicitly *not* part of the v5.5.0 formalization.
 
 **v5.5 → `2.2` (framing enforcement).** `2.2` adds two **required-at-2.2** elements — the `framing` enum field and the `## TL;DR` body section — gated identically to the v2.1 mechanism: the new requirements fire only on `brief_version ≥ 2.2`, so every existing `2.0` / `2.1` brief still validates (forward- and backward-compatible). Because adding required elements is a breaking change for any producer that declares `2.2`, this is a controlled version bump under the breaking-change protocol: downstream producers (e.g. a Tier-2 per-app producer) that emit `brief_version: "2.2"` MUST also emit `framing` + `## TL;DR`. The framing enum is additionally enforced on *any* version when the field is present (`BRIEF_INVALID_FRAMING`). The three framing-alignment layers (framing field, `brief-reviewer` memory-alignment dimension, obligatory TL;DR) implement the `CLAUDE.md` cross-cutting invariant. Note: the *plugin* version bump + CHANGELOG entry for this schema change land at the coordinated release (matrix §S10), separate from this schema axis.
 
+**Pre-2.2 briefs receive zero framing enforcement (producer-elective defense).** The framing-alignment defense is gated at `brief_version ≥ 2.2`, so a brief declaring `2.0` or `2.1` gets **none** of it: `framing` is optional and a missing value is not an error, the `## TL;DR` section is not required, and the `brief-reviewer` memory-alignment dimension scores N/A. The backward-compatibility this buys is deliberate, but it also means the framing defense is **producer-elective**: any producer can sidestep the entire defense — deliberately or by shipping a legacy template — simply by declaring `brief_version: "2.1"`, and the pipeline raises no signal by default. This is a documented property of the contract, not a bug. Two remedies close it for a given consumer: (1) require upstream producers to emit `brief_version: "2.2"` (which forces `framing` + `## TL;DR`); or (2) pass the opt-in **`--min-brief-version <ver>`** flag to `/trekplan` or `/trekresearch` (forwarded to the validator as `--min-version`), which raises a `BRIEF_VERSION_BELOW_MINIMUM` **warning** — never a block — when a brief declares a version below the floor. The flag defaults to off, so the N-1 compatibility window for `2.0`/`2.1` briefs is preserved unless a consumer explicitly opts into the stricter floor.
+
 **Failure modes:**
 - `BRIEF_NOT_FOUND` → consumer halts with a usage message
 - `FM_MISSING` → file has no frontmatter; halt

docs/command-modes.md

@@ -24,6 +24,7 @@ Always interactive. Phase 3 is a section-driven completeness loop (no hard cap o
 | `--external` | Only external research agents (skip codebase analysis) |
 | `--fg` | No-op alias (foreground is default since v2.4.0) |
 | `--gates {open\|closed\|adaptive}` | (v3.4.0) Autonomy-checkpoint policy. Default `adaptive` |
+| `--min-brief-version <ver>` | (S18) Warn — never block — if an attached `--project` brief declares a version below `<ver>` (e.g. `2.2`), i.e. sidesteps framing enforcement |
 | `--profile <name>` | (v4.1.0) Model profile for the research phase. |
 
 Flags combine: `--project <dir> --local`, `--external --quick`.
@@ -37,6 +38,7 @@ Flags combine: `--project <dir> --local`, `--external --quick`.
 | `--research <brief> [brief2]` | Enrich with extra research briefs beyond what is in `{project_dir}/research/` |
 | `--fg` | No-op alias (foreground is default since v2.4.0) |
 | `--quick` | Plan directly (no agent swarm) |
+| `--min-brief-version <ver>` | (S18) Warn — never block — if the brief declares a version below `<ver>` (e.g. `2.2`), i.e. sidesteps framing enforcement |
 | `--export <pr\|issue\|markdown\|headless> <plan>` | Generate shareable output from existing plan |
 | `--decompose <plan>` | Split plan into self-contained headless sessions |
 | `--gates {open\|closed\|adaptive}` | (v3.4.0) Autonomy-checkpoint policy. Default `adaptive` |