docs: fix typos, grammar, and terminology consistency (copyedit pass)

[bblietz]

Summary

Mechanical copyedit pass across the docs: fixes typos, doubled words, grammar defects, and product-term casing/spelling inconsistencies surfaced by an automated + manual audit. 77 files, 126 word-level substitutions, no structural changes. Every change was individually verified against source; nothing inside code fences, API field names, enum values, or asset paths was altered.

Tier 3 - typos & grammar

• Misspellings: photograpy→photography, quartely→quarterly, intall→install, mechansim→mechanism, contactually→contractually, subscritpion→subscription, cancelation→cancellation, availabilty→availability, occuring→occurring, responsiiblwe→responsible, encounted→encountered, paramaters→parameters, requried→required
• Doubled words removed: "is is", "the the", "node node", "be be", "that that", "will will", "to to", "and and", "of of", "or or", "this this"
• Wrong/missing words: affect vs effect, "Building apps requires", "returns an Associative array", "authority to submit", "fewer than 1,000", "Not all devices support...", "live linear", present-tense "identifies", "valid WAV file", "Specifies how"

Tier 2 - terminology consistency

• Brightscript → BrightScript (36 prose/label instances; confirmed against the corpus-majority BrightScript Debugger> prompt casing)
• RokuOS → Roku OS (prose only; preserved the /RokuOS/Artwork/ firmware asset path)
• WiFi / Wifi → Wi-Fi (prose only; preserved lowercase wifi feature-check value and the <wifi-mac> ECP tag)
• Scene Graph / Scenegraph → SceneGraph
• Prose US spelling: labelled→labeled, prose cancelled→canceled, grey→gray

Deliberately preserved (real API surface, not errors)

• Nabu Cloud organisation entity name
• Roku Pay cancelled JSON/XML field name
• BBFC behaviour ratings enum value

Out of scope

deep link / deep-link / deeplink variants were left alone: the hyphenated compound-adjective form vs the open noun form are both correct, so this needs a per-instance style decision rather than a sweep. A separate set of factual contradictions (e.g. HEVC bitrate 40 vs 25 Mbps, Verimatrix DRM listed then declared removed, mediaType vs feed-type casing) was also found and needs SME sign-off on the correct values; not included here.

Test plan

• Rendered spot-check of changed pages (SceneGraph reference, Roku Pay, analytics reports, media specs)
• Confirm no code samples, field names, or asset paths were altered