docs: fix dangling versioning pointer, align Feature spelling, add ISA design-doc aliases

[anikinsasha]

Three small documentation consistency fixes. All three are text-only; no behavior, no code.

1. OPERATIONAL_RULES.md § Versioning is a dangling pointer

LifeosSystemArchitecture.md:305 and Skills/SkillSystem.md:218 both name OPERATIONAL_RULES.md § Versioning as the home of the standing three-level version rule. That section does not exist. The shipped install/USER/CONFIG/OPERATIONAL_RULES.md stub has exactly four sections — Tool & environment preferences, Repo conventions, Deployment, Vendor-specific rules — and no Version field.

The real canonical home is LifeosSystemArchitecture.md § Versioning itself. Line 303, inside that very section, already says the standalone Ledger doc was "folded into this section, which is now the canonical reference." Line 305 was pointing away from its own section, four lines below the heading it belongs to.

There is also an architectural reason not to fix this by creating the missing section: OPERATIONAL_RULES.md is a per-principal USER file (one of the @-imported identity files), shipped as an empty stub. A system-wide rule placed there would not survive into any install.

• LifeosSystemArchitecture.md:305 — the trailing sentence now states that this section is the standing rule, instead of forwarding elsewhere.
• SkillSystem.md:218 — see OPERATIONAL_RULES becomes see `LifeosSystemArchitecture.md` § Versioning.

2. MAJOR.MINOR.PATCH → Major.Feature.Patch in CreateSkill

skills/CreateSkill/SKILL.md:428 says MAJOR.MINOR.PATCH, while both system docs say Major.Feature.Patch and explicitly call out that the middle number is "Feature, not 'minor.'"

CreateSkill's own workflow files already agree with the system docs — Workflows/CreateSkill.md:326 and Workflows/UpdateSkill.md:136 both use patch/feature/major. Line 428 is the lone holdout in the tree, so this normalizes it.

3. The ISA skill can't be routed to by its own name

skills/ISA/SKILL.md currently reads:

USE WHEN ISA, ISC, ideal state, ideal state criteria, project specification, hill-climb, articulating done.

"ISA" and "ISC" are three characters each, and the USE WHEN parser drops phrases shorter than six characters. The indexed trigger set is therefore only the multiword phrases — the skill's two primary names match nothing. Separately, "PRD" is a trigger nowhere in the tree, so "design a PRD" (a very common way to ask for exactly this artifact) matches no skill at all.

This adds PRD, design doc, and design architecture:

• "design doc" (10 chars) and "design architecture" (19) clear the six-character filter and index normally.
• "PRD" stays below the filter, but it is still read by the model when it scans skill descriptions, and it costs three characters to carry.

Additive only — no existing trigger is changed or removed, so no current routing behavior is altered. The description goes from 440 to 478 characters, within the 500-character recommendation in SkillSystem.md (and well under the 650 hard ceiling).

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Split into two commits so the objective fixes (1 and 2) can be taken independently of (3), which is more of a judgment call.

I understand the public repo is generated from a private source tree and that fixes are ported rather than merged — happy to reshape any of this if the private-side wording differs.

Verification, run against the tree after the change:

rg -q OPERATIONAL_RULES LifeOS/install/LIFEOS/DOCUMENTATION/LifeosSystemArchitecture.md LifeOS/install/LIFEOS/DOCUMENTATION/Skills/SkillSystem.md
rg -q MINOR LifeOS/install/skills/CreateSkill/SKILL.md
rg -q PRD LifeOS/install/skills/ISA/SKILL.md

First two return nothing; the third matches.