[proggeramlug]

Closes #4511.

Problem

• escape() / unescape() (ES Annex B B.2.1, still standard and present in Node) were undefined — bare calls threw ReferenceError. qs (qs/lib/utils.js) uses them for %uXXXX decoding, so any app pulling in qs (e.g. via stripe) hit this.
• The Node global object was likewise unresolved — (global as any).x emitted Warning: unknown identifier 'global'. (globalThis already worked.)

Approach

Both are routed through Perry's existing reflective globalThis function-value path — no dedicated HIR Expr variant (lighter than the ~20-file encodeURI-style approach; correctness, not a fast path, is what's needed here).

• runtime (builtins/globals.rs): js_escape / js_unescape implement Annex B encoding over UTF-16 code units — code units <256 → %XX, else %uXXXX; astral scalars emit their surrogate pair (matching Node). unescape reassembles UTF-16 units before decoding so %uD835%uDFD8-style pairs recombine.
• runtime (global_this*.rs): register escape/unescape thunks in GLOBAL_THIS_BUILTIN_FUNCTIONS; install a self-referential global property on the globalThis singleton (global === globalThis).
• HIR (analysis/builtins.rs): add escape/unescape/global to is_builtin_global_value_name so bare calls and value reads resolve to globalThis.<name> instead of throwing (also makes them is_known_global_identifier_name).
• codegen (expr/helpers.rs): add the three to is_global_this_builtin_name; exclude global from the function-typeof set so typeof global === "object".

Verification

Byte-identical to Node on both the default auto-optimize and PERRY_NO_AUTO_OPTIMIZE=1 paths, including non-ASCII (café), BMP (☃), astral (𝟘 → %uD835%uDFD8), malformed/partial escapes (%, %2, %zz, 100%), rebound values (const e = escape), and local shadowing (function escape(){} / const global = {} correctly win). All perry-runtime / perry-hir / perry-codegen tests pass; cargo fmt --check clean. Adds test_gap_escape_unescape_global_4511.ts.

Note: the issue's "Expected" shows a%20b%2Bc, but + is in escape's unescaped set — real Node returns a%20b+c, which this matches.