refactor(ethos): rename Boil the Lake principle to Boil the Ocean

Reframes the completeness principle so the ocean (the complete thing) is the
goal and lakes are the boilable units you ship on the way there. "Don't boil
the ocean" was right when engineering time was the bottleneck; AI killed that
bottleneck, so the ocean is now the destination.

Resolves an existing split: the scope_appetite psychographic, archetypes, and
the completeness intro flow already used "boil the ocean" as the
complete-implementation pole while the named principle still said "lake".

Sources only: ETHOS.md philosophy, CLAUDE.md, README.md, the preamble
resolvers, and the plan/autoplan/document-generate templates.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -137,7 +137,7 @@ gstack/
 ├── setup            # One-time setup: build binary + symlink skills
 ├── SKILL.md         # Generated from SKILL.md.tmpl (don't edit directly)
 ├── SKILL.md.tmpl    # Template: edit this, run gen:skill-docs
-├── ETHOS.md         # Builder philosophy (Boil the Lake, Search Before Building)
+├── ETHOS.md         # Builder philosophy (Boil the Ocean, Search Before Building)
 └── package.json     # Build scripts for browse
 ```
 
@@ -776,8 +776,10 @@ When estimating or discussing effort, always show both human-team and CC+gstack
 | Research / exploration | 1 day | 3 hours | ~3x |
 
 Completeness is cheap. Don't recommend shortcuts when the complete implementation
-is a "lake" (achievable) not an "ocean" (multi-quarter migration). See the
-Completeness Principle in the skill preamble for the full philosophy.
+is achievable. Boil the ocean — the complete thing is the goal; only genuinely
+unrelated multi-quarter migrations are separate scope, never an excuse for a
+shortcut. See the Completeness Principle in the skill preamble for the full
+philosophy.
 
 ## Search before building