Expand unit 6b: includes, computed constants, inline functions

[EvanWinget]

What changed

Docs only, plus one line-item in the reference fetch script. No spec or implementation contact, so no spec section applies. The unit 6b bullet in docs/execution-plan.md is rewritten: scope expands from a bare include mechanism to source-level include of shared constants and functions, computed compile-time constants, and inline functions, and the unit is resequenced ahead of unit 7. Unit 7's style constraint is widened to admit the new surfaces. tools/fetch-references.sh gains the two corpora the decision cites.

Why

A census of the two deployed-puzzle corpora (tibetswap b82e921, chia-gaming cdab9c9) found:

• Every production puzzle file in both corpora imports shared definitions (all 12 tibetswap puzzles, all 19 chia-gaming non-test puzzle files, about 200 import and include statements in the latter).
• tibetswap defines 124 of 136 functions inline, the single cheapest on-chain cost lever and directly relevant to Phase 4's vbyte measurements.
• chia-gaming uses computed compile-time constants (defconst) 36 times.
• let is effectively unused: two occurrences across both corpora, both in test files, so it stays out.
• assign appears only in chia-gaming (about 20 on-chain uses), so it stays held on unit 7 evidence, now with a pre-registered trigger.

The census also corrected the prior deferral's premise. chia-gaming did not abandon source-level import: its imports are universal, and the compiled-sibling hash plumbing the old bullet described lives in its build layer, not its language. That import mechanism stays deferred, with bitlisp-compile -T covering the need manually.

Decision by Evan, 2026-08-16, skeleton change under ground rule 6.

Read order

1. docs/execution-plan.md (the unit 6b bullet, then the unit 7 style constraint)
2. tools/fetch-references.sh

Verify independently

tools/fetch-references.sh
# includes are universal (expect 22 statements across all 12 tibetswap puzzles):
grep -rc "(include" --include="*.clsp" references/tibet/clsp
# tibetswap inline ratio (expect 124 vs 12):
grep -rhoE "[(]defun-inline |[(]defun " --include="*.clsp" --include="*.clib" references/tibet/clsp references/tibet/include | sort | uniq -c
# let is test-only across both corpora (expect 2 hits, both under clsp/test):
grep -rnE "[(]let[*]?[ (]" --include="*.clsp" --include="*.clinc" references/chia-gaming/clsp references/tibet
PATH=.venv/bin:$PATH ci/lint/lint.sh