Docs: name the force function (uniform mechanism, local voice)

FORCE_FUNCTION.md

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+# Language as a force function
+
+A force function is a constraint that produces an outcome regardless of anyone's memory or good intentions. A car that won't move until the seatbelt clicks is a force function. This page explains the sense in which chalkline makes a team's language one, and — just as important — the sense in which it deliberately does not.
+
+The distinction matters most at organization scale, where dozens of agents and hundreds of people write on a company's behalf. Unaligned language stops being a style problem there and becomes a structural one: contradictory product terms, brand drift at machine speed, and legal wording quietly paraphrased in a rewrite nobody reviewed.
+
+## The force is the consult contract, not the content
+
+chalkline aligns *how* a team binds its language. It never dictates *what* the language is.
+
+**Uniform — the mechanism a whole organization can share:**
+
+- Agents consult the references before writing, and say so instead of guessing (`AGENTS.md`).
+- `must` beats `should`; more specific beats more general. Precedence is declared, not improvised.
+- Text under an **"Exact wording"** heading survives every rewrite byte-for-byte.
+- Conflicts and gaps surface to a person; they are never resolved silently.
+- An agent may not present output as "on brand" if it could not read the references.
+- Every rule carries a provenance line: who approved it, from what, and when.
+- Calibration pairs turn the approved voice into a regression check, so drift is caught in review rather than discovered by a customer.
+
+**Local — the content each team keeps sovereign:**
+
+- The voice, the terms, the banned words, the channel rules. chalkline ships none of these and holds no opinion about them.
+- Each team fills the same substrate with its own language. A support team and a legal team in the same company can run identical mechanics over entirely different words.
+
+So an organization can standardize *the way language is bound* without standardizing *the language itself*. That is the whole point: alignment of the mechanism, sovereignty over the content.
+
+## Why this is not a one-size-fits-all plan
+
+The tempting mistake at enterprise scale is to answer "align our language" with a mandated agent, a central voice, an enforcement platform, or a taxonomy everyone must adopt. That is the opposite of what works, and chalkline refuses it on purpose:
+
+- **No shipped voice.** The tool never tells you how to sound. If it did, it would be one company's style guide wearing a template's clothes.
+- **No mandated agent or runtime.** The contract is plain markdown routed by `AGENTS.md`. Any AGENTS.md-aware tool can honor it; none is required. The mechanism spreads by being small and copyable — the way markdown and robots.txt spread — not by decree.
+- **No central authority over people or teams.** chalkline records a team's own approved judgment. It does not grant permissions, prove an agent complied, or override the humans who own the words. See [Operability](OPERABILITY.md) for what it explicitly does not own.
+- **No speculative machinery.** Cross-repository precedence, multi-brand configuration, and evaluation runners are not shipped. They are earned by field evidence from real teams, or not built. See [Contributing](CONTRIBUTING.md).
+
+The force function is strong precisely because it is narrow: a shared, inspectable, portable way to make approved language bind — with the words left entirely to the team that has to stand behind them.
+
+## Where this fits
+
+- **[README](README.md)** — what chalkline is and how to set one up.
+- **[Operability](OPERABILITY.md)** — the loop that keeps a system useful after setup, and the boundaries of what chalkline owns.
+- **This page** — why the result behaves as a force function without becoming a mandate.

README.md

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 **Snap a line before your agents build.**
 
-Your team runs on language now: it's how you brief agents, how agents write to your customers, and what your product's words are supposed to mean. chalkline turns the part of that your team can actually agree on — voice, terminology, vocabulary, channel rules — into a small writing system agents consult instead of guess at. A chalk line is the first tool on a build site: snap it once, and every cut after lands straight. This is that, for your team's language.
+Your team runs on language now: it's how you brief agents, how agents write to your customers, and what your product's words are supposed to mean. chalkline turns the part of that your team can actually agree on — voice, terminology, vocabulary, channel rules — into a small writing system agents consult instead of guess at. A chalk line is the first tool on a build site: snap it once, and every cut after lands straight. This is that, for your team's language. It aligns *how* your language binds — the same contract every agent consults — while leaving *what* you say entirely to you; see [Language as a force function](FORCE_FUNCTION.md).
 
 ## The problem