Converge Grease intent, source pin, and archaeology

[isomorphisms]

Reconciles the current Grease state against the Oils branch graph and the later ish / Odriç split.

• advances source/ from e9a54ad to current oils:grease/main 8052868
• records CURRENT / SUPERSEDED / EXPERIMENTAL / UNDECIDED decisions with provenance
• inventories every Grease Oils branch, including the ten idea branches that are only labels on the baseline
• distinguishes the three promoted quick wins from abandoned branch topology
• records the merged readable Unicode behavior (⟦ … ⟧, ∧, ∨, ¬) and its focused executable receipt
• records Ithon and ICKY as experiments rather than silently promoting them into present Grease semantics
• makes the later responsibility split explicit: Grease remains the Oils/YSH-derived working/reference shell; ish is the separate descendant intended to be written in Odriç
• adds a top-level grease-receipt workflow that checks out the pinned source and runs Oils' substantive cpp-spec job without the separate publishing step
• leaves the unrelated SMS-service PR and the ish successor branch untouched

Executable evidence:

• historical readable-syntax head ac8d766: substantive cpp-spec passed; only the later publish-html step failed
• tested and merged commits have identical lexer and focused-spec blobs for this feature
• canonical top-level receipt run 33708983086 completed successfully on tested head 4de2e036788e8c9a6a959ae72ccc1786bdb5f1d5 against corrected pin 8052868
• after the two provenance-only follow-up edits, receipt run 33763762783 completed successfully on current head fa2ed54deaff26042fd90cac6ccb575ba04e3aca

No protected/main branch is merged by this pass.